At last, I am here to speculate on the power & implications of the final previews. I don't play online so I haven't tested any of these.
So, gaining a $5 cost is good, but Importer seems very likely to delay the gain for a shuffle, while skipping a shuffle itself. I think this works for $5 cards that you want to eventually have in your deck but don't need immediately. Like, I don't know, Groundskeeper. Overall I think this is a weak card.
Courier reminds me of how hard it is to trigger Swashbuckler or Settlers. It turns out that your discard pile is just empty like half the time. And what if the top card of your deck isn't an action, then Courier is terminal! In the best case, you have a sloggy deck that doesn't shuffle very often, or maybe you have a synergy like Mill. Quite weak.
Royal Galley has tricked you all by reminding you of Throne Room. Instead it reminds me of Caravan or Ghost Town. This turn, it draws a card and lets you play an action, effectively +1 card +1 action. Next turn, it's effectively +1 card +1 action again, but the extra card & action are spent on the same card you played the previous turn. And it requires collision with a non-duration action. I think this is a lot weaker than Throne Room, despite the extra draw.
Note, though I judge these cards to be weak, I very much like weak cards. They pose challenges.
I really like Family of Inventors, but since its effects affect all players I think it may not be very strong. You get access to the benefit one turn before your opponent, that's something. Gives 2nd player an advantage in the first shuffle. Otherwise, it relies on some asymmetry in strategies. One neat move is to put them on Wizards, preventing your opponent from remodeling Liches into Province+Duchy.
Among the previews, I really like the split piles, and look forward to seeing the last two. Split piles were low key my favorite mechanic from Empires, and these ones seem even more dynamic.