First impressions, without reading anything else in the forums about it all...
Archive - I love it. It's relatively simple, but creates deep tactical considerations. I'm shocked that I haven't seen any fan cards that do this. A fun thing is that the set aside cards can be used to track whether it should stay in play, which would otherwise be a small issue for a multi-turn Duration. Non-terminal means you can stack these, and they even make it easier to chain multiples on the same turn (or save them for later if you prefer). Really cool.
Charm - Treasure Woodcutter, or a Duplicate variant. I can see this as a mega-turn card like HoP, given the right board... specifically, when Prince or Peddler are also in the kingdom, a bunch of Charms could gain all the Provinces. But it could also be used to empty other piles, of course. I think this will be a lot more useful than Talisman. Very neat.
Patrician/Emporium - Patrician is like Vagrant, except it usually draws good cards instead of junk. The downside is that "good" actually means "expensive". Even trim decks tend to have a bunch of sub-$5 components, so Patrician is not necessarily reliable. Even so, I think I'd prefer it over Vagrant most of the time. And then there's Emporium... Neither card here directly references the other, but they synergize nonetheless. Patrician makes it more likely that you'll be able to trigger Emporium's on-gain. Emporium is another potential target for Patrician to draw. This particular split pile isn't mind-blowing to me, but it's a nice combination. In this case, I don't think there's a thematic connection between the two cards, but they thematically make sense for what they do. Patricians are high class, so they bring expensive stuff with them. Emporiums are places of commerce, so you should open them in places with high traffic and activity.
Encampment/Plunder - Plunder is a simple Silver+, giving 1VP when you play it. It is essentially Monument as a Treasure. Being that similar means maybe it wouldn't be that interesting as its own pile, or it might have problems (since it is essentially be non-terminal), but this is mitigated by Encampment. Not only are there fewer Plunders to go around, but they aren't accessible early in the game, and they're still somewhat tough to pick up because of Encampment being returned to the pile. Encampment is itself really interesting. It's a powerful one-shot for $2. I think I'm going to have a hard time figuring out when that alone is worthwhile, but then there's the possibility of it
not being one-shot. No doubt you will often be faced with the option of playing Encampment without Gold/Plunder in hand. Is it better not to play it so you can keep it for a safer turn? Do you play it and hope you draw the needed Treasure? If that's not a possibility for whatever reason, could it be worth giving up Encampment just for its bonuses? Or if you do have the treasure in hand, could it be good to forego the reveal and let it return to its pile, blocking Plunder? So many considerations! I'm not sure of the thematic narrative. Buying an Encampment is like setting up an army for your legions? But your legions will desert you if you don't show them you can pay?
Engineer - Obviously better than Workshop, but it doesn't seem
that significant to me. For a slightly higher cost, you get a nice bonus for when you no longer need it, letting you replace this unwanted card for something more useful. But until you do that, it's just a Workshop. I wonder how often it will be a good play to buy it and trash it immediately. That would be like delaying the $4 you would have gained for a shuffle in order to get a bonus gain... hm. My first impression is that this is marginal, but it may be a key interaction for winning certain splits.
Forum - One of the more vanilla cards. a 1-card improvement on Warehouse, letting you sift and cycle without reducing handsize. The on-buy doesn't seem so significant, but it makes its cost a little lower.
Legionary - A brutal attack, strong enough that it requires a Gold reveal to trigger (thematically fits with the idea of paying your military, as with Encampment?). Interesting that it produces +$3 itself. It's worth noting that Legionary doesn't suffer the same drawback as Margrave in multiples, since you can decline to reveal Gold. Sounds good, though I think Margrave will prove stronger overall thanks to its set of vanilla bonuses.
Overlord - It can copy cards that cost $5, which is significantly better than BoM. Moreover, the fixed limit means you could potentially copy extra expensive cards like King's Court or Prince if you have some cost reduction. Fun meta note, Overlord allowed Donald X. to sneak in some rules clarifications for BoM regarding new stuff in Empires like Encampment, Crown and Colonnade.
Sacrifice - Sounds good. You usually don't want to trash actions, so the bonus for doing that is strong. The bonus for trashing Treasure is weaker than either Moneylender or Spice Merchant, which makes sense since Sacrifice is a lot more flexible. Trashing Estates is great, Duchies OK, more expensive VP cards not so much. But Estates is the big thing. I think this will be a good counter to Looters.
Wild Hunt - You'll pick the first option most of the time since you don't want to gain a junky Estate, in which case it's basically an expensive Smithy. But sometimes the gathering VP will be tempting... and when's the right time to pull the trigger on that? I have no idea. Man. Being able to play a bunch of Wild Hunts in one turn will be pretty good, as you'll be able to pick up a bunch of VP all at once. In that case though, it's still just +1VP per play of Wild Hunt (including the last one, if you count the Estate). It would be more efficient to let it accumulate even more, but that risks another player scooping the VP out from under you. Still potentially doable if they can't (or are unlikely to) play a Wild Hunt on their next turn. I like this a lot. Gathering cards are so neat.
Advance - Suddenly Ruins are valuable?? This really shakes up the game, potentially making expensive key cards a
lot easier to pick up.
Annex - Seems useful in a slog, when your deck is a mess and you're having trouble ending the game. Annex is <8> for a Duchy, which might be a good deal if you're having trouble hitting a full $8 or even $5 on a single turn. The shuffle effect may improve your hands for the next few turns, making it easier to hit $8 later. Overall, looks niche to me.
Banquet - It basically Cache-ifies other cards, making something cheaper by attaching 2 Copper to it. Fun use: Banquet for Cache to gain 4 Copper total. There are probably some edge cases where you'll want to use this to gain a card that costs $3 or less (e.g. Gardens-Beggar).
Conquest - Designed for SCSN, no doubt.

Probably helps Big Money strategies a lot. The stacking self-synergy is interesting. If you have $12 and 2 Buys, it's worth as much as Province but comes with 4 Silver instead of a green card. $18 and 3 Buys, you can get 12VP and 6 Silver, which matches 2 Provinces in VP. $24 and 4 Buys, it's 20VP and 8 Silver, which is more than 3 Provinces and matches 2 Colonies, a great deal if you want all that Silver. But do you want all that Silver? It's an interesting parallel to Triumph. It has higher (opportunity) cost and only counts Silver, but it also gains two cards each time you buy it so it grows more quickly. Neat.
Delve - Makes Silver cheaper to buy. Simple enough. I don't expect this to make a difference on most boards. It could make Silver-favouring cards (Feodum and Conquest?) more viable though, and it may give an edge to Big Money strategies where they otherwise wouldn't be competitive. Hmm.
Donate - Wow, this turns the game on its head. When Donate appears, you'll pretty much always want to buy it once. But when? Early turns spent prepping for the Donate turn will be critical. It's designed so that you can buy it and get full benefit on any turn, which is nice. It reminds me of Chapel, and I wonder how the two will compete. I'm tentatively guessing that Donate will trump Chapel most of the time, but the <8> cost makes it hard to judge.
Ritual - As a VP gainer, it's more powerful than Bishop for trashing cards that cost more than $4 or more, but you have to keep buying it and you accumulate dead cards in your deck that Ritual can't effectively remove. I really like Bishop, so I think this will be fun too.
Salt the Earth - It's a way to end the game more quickly. Will probably be used primarily to empty piles quickly. Players will have to watch each other carefully. As the current points leader, is it worth the $4 and Buy to trash a Province and take another step closer to the end, or should you continue building your deck lest another player overtake you? I like it.
Tax - Sounds like a blast. The setup potentially gives the second player an advantage (they can mirror the first player and avoid the Debt) and the Event as a whole is basically one big catch-up mechanism. The first to buy each VP card will take at least 1 Debt from it. If your deck is stronger, you're probably buying more cards and thus more likely to run into placed Debt. If you're behind, you can buy this to try to stymie the leading player. Granted, the leader could buy this as well, but it could be self-hindering unless players are pursuing very different strategies.
Wedding - It has a Debt cost, haha. In games where I want Gold, I think I'd buy it via Wedding most of the time. The +1VP is nice, and the lower coin cost makes it easier to pick up anyway. Games with Wedding will likely feature early Gold gains, which could really change the dynamic of the game. Sounds fun.
Aqueduct - It kind of turns VP cards into Gathering cards? Tokens accumulate, tempting players to buy Victory cards earlier than usual. Unless nobody ever gains Silver or Gold.
Arena - Encourages opening with two terminals, and overloading on terminals or just actions in general. Sometimes you might skip playing an action card just to trigger Arena. I like it.
Bandit Fort - Well, we didn't like Silver or Gold anyway.
Basilica - Encourages underspending, and gives you something to do with a plethora of +Buy. Again, sounds fun.
Baths - I bet some inexperienced groups will just spend the first several turns passing until all the VP is gone and think Baths does nothing but delay the start of the actual game. I wonder how often it'll actually be the right call to skip a potentially productive turn for Baths VP. I expect it'll more often end up being a consolation prize for a bad turn. I see interesting synergy with Mission. Notably, you could just buy Mission to get 4VP tokens for $4.
Colonnade - Weird! So it encourages buying multiples of the same card, and the wisdom of that will depend on the cards available. In general though, it encourages buying more actions, which is nice after all those various cards that boosted Big Money.
Defiled Shrine - I like this more than Aqueduct (not that I dislike Aqueduct). I expect that the VP growth will be better than Aqueduct on most boards, at least among experienced players. And unlike Aqueduct, you have to commit more to get VP from Defiled Shrine, as opposed to it being a bonus on something you'd probably buy eventually anyway. I see that Defiled Shrine can steal VP from Gathering cards.
Labyrinth - Simply encourages +Buy. Not mind-shattering, but they can't all be so.
Mountain Pass - OK, so this is the card with bidding. I'm guessing that this encourages buying a Province early, for the advantage of being the last to bid. 8VP is significant, and Debt does make it an easier "buy". I can't see it ever being a good idea to bid <40> on this in a real game. The unlikely edge case I can come up with is if Salt the Earth has already drained most of the pile, so securing this Province will get you the win. Hm, a similar alternative is if this 8VP will guarantee you at least half of the total VP available in the game, which is unlikely since there will usually be 7+ more Provinces to go (and with Empires, probably more ways to get VP tokens). So what's an actual appropriate bid? Province is 6VP for $8 and Colony is 10 VP for $11. The average of those is 8VP for $9.5, but this is in debt and it's VP tokens with no dead card attached... <10> sounds like a great deal, and even up to around <14> is probably still good? Man, I don't know. Could also flip this around and wonder what the lowest reasonable bid is... I guess you may not want any debt at all if you have a very precise plan to empty piles for a win, but that's tough to work out from just a starting hand.
Museum - Automatic Fairgrounds, haha. Fairgrounds is fun, and this guarantees that drive to diversify. I am a fan.
Obelisk - Bold rulebook move, not specifying a randomization process. It shows a respect for and trust in the players, which may not always be deserved.

This is a very simple effect that can really skew strategy, pretty much guaranteeing that there will be competition over a given pile. Even the weakest cards may be attractive if they are the chosen one!
Orchard - Another Fairgrounds-like Landmark, with a touch of Vineyards (especially in the name). I like it, though I like Museum more.
Palace - Simple enough. Maybe you'll keep some extra Copper around, depending on how many Gold you expect to gain. If you have no extras without a set, then Palace is essentially 1VP per basic Treasure.
Tower - Weird card. It encourages you to try to empty piles where you're winning the split already, but you might also dive in where you're losing if it seems inevitable, just to mitigate the difference. Creates some very interesting interaction and makes 3-pile endings more likely. Sounds great.
Triumphal Arch - Interesting. This encourages going deep on two Action cards. Incredible if there's a strong 2-card combo available, but still has a heavy pull on the game without. I really like this too.
Wall - Gotta get that thin deck. Junkers are more powerful, which is a little scary, but it sounds really fun anyway.
Overall, this looks awesome. Just wonderful. Great stuff.