So here are my thoughts :
Altar : I underrated this card so much... it's really great for engines, where there are a lot of $5. The trashing is often good, but sometimes a penalty. Note that altar do not have the "if you do" clause, so you'll sometimes reveal a hand of nothing and gain a free $5 card.
Armory : Better than I expected. I like the tactic component here (gain the card you'll need for now or for the next turn...
Band of misfits : Rather weak, seriously. But sometimes can really shine (remodel, village-draw, etc). Otherwise very interesting card.
Bandit camp : It seems very powerful to me, I lost a game where my opponent only bought bandit camps and money, that's disappointing.
Beggar : I love copper engines and I think the game need more defenses to attack. So obviously beggar is a very cool and interesting card.
Catacombs : I'm not a huge fan of this card. It's not bad, but not very innovative compared to other dark ages cards. The on-trash effect is weird and is infrequently used. But we need terminal draw in all sets...
Count : Not so difficult to understand, all effects synergize. The trashing ability is less powerful than I thought first. Otherwise another powerful and interesting card.
Counterfeit : Very very strong, for engines as well as Big money games. I like the versatility and the choices it offers.
Cultist : Great attack card, not as boring as witch/mountebank/goons/etc. And the on-trash effect make it so interesting !
Death cart : Swingy, but a terminal $5, even one shot, is strong. Ruins slow the deck cycling though.
Feodum : I love this one. A real headache because we are always faced with the choice to trash or not a feodum (usually it depends on the kingdom of course).
Forager : Nothing special to say, very good trasher overall.
Fortress : It's funny to use it as a target for all trashers when you got rid of all your coppers and estates. Not the best $4 village, but a very fun one.
Graverobber : Beside the combo with treasury, from the few games I played with graverobber it wasn't very strong. But I guess it is great in engines with villages.
Hermit / Madman : One of my favourite of the set, but it seems to be a trap very often. The trashing ability is very weak (except in cursing games, where it's almost as good as Jack). The mandatory gain can be a flaw... and most importantly the way to gain madman is problematic : early it's easy, but madman won't be great with so few good cards. Later it will be pretty difficult to gain the madman (but this time it will be great). Also, against handsize reducers madman is really bad.
Hunting grounds : Very strong as I thought. But like catacombs I'm disappointed that the on-trash effect is not very often useful.
Ironmonger : The randomness make it, like Tribute, risky. However, I think Ironmonger is more often controllable, and it's interesting to use instead of village when you need +2 actions.
Junk dealer : Simple and solid. I'm almost surprised to see such a simple card in an expansion like Dark Ages ^^
Knights : For the time being, my favourite card(s) of the set. I have a particular love for Molly and Josephine. I really like how sometimes they prevent mirror matches.
Marauder : Sea Hag is better.
Market Square : Usually weak, because the effects anti-synergize. But as a source of +buy market square is nice.
Mystic : An average $5 cards, now you can do all the things you always wanted to do with wishing well.
Pillage : I don't know if this is very strong. The attack is brutal but you get no direct profit from it, two spoils are not so good...
Poor house : Sometimes incredibly powerful, other times useless. I like the $1 cost, especially when upgrade is in the kingdom ! ^^
Procession : Very interesting and tricky card. I really like it !
Rats : A "double-edged" card, and I love how it's thematic. One of my fav of the set too.
Rogue : I love this one, because you are forced to do one of the 2 things... and if you don't gain that workshop from the trash, you can't attack your opponent anymore. Otherwise rogue is not so bad !
Sage : Great in engines with no trashing, and in opening. But very frustrating when you hit a province (and it happens very often).
Scavenger : Nice scheme-chancellor, a solid $4.
Squire : At first, I thought it was the best $2 of the game. Now, I think it's near to the worst (ok I exaggerate a bit) : the lack of +card is terrible and usually you don't need terminal +2 buy or terminal silver-gainer. I never used the on-trash effect though.
Storeroom : Honestly I think it's an excellent $3, probably a little below the top 10. It's a great card for deck cycling and combos.
Urchin / Mercenary : It's very easy to gain the mercenary, which is quite strong, but get progressively worse later during the game... like Hermit, not alxays indispensable.
Vagrant : Very good $2. Better than scout !
Wandering minstrel : One of the worst $4 village, I think (still pretty close). It's quite insignificant in games with trashing, and otherwise you don't really want to discard your treasures.
My favourites are Knights, Rats, Feodum, Hermit and Rogue.