So many new cards; I'll post my first impressions of my favorites.
Forum: I've been hoping for a card line this for a while. We really have needed more sifters that preserve your handsize. I really like the cost, how yes it costs $5 but not a buy. I foresee jokes about the name.
Engineer: I like how the debt cost helps balance this card, not because you would normally pay less for it up front, but because you can't do crazy things with trashing Engineers to gain Engineers and then play them to gain more cards.
Delve: I want to add "like Silver" to the end of the rulebook entry.
Sacrifice: I guess the flavor fits in with Tribute rather than Iron. I do like how it does slightly different things than similar cards. And it provides a reason why you might actually want to trash Estate-Crowns if that worked, so that question didn't go to waste. It's cool to finally have a trashing village.
Ritual: I love Bishop, so I think I'll like this. It's great if you have a way to get rid of those curses. I can see it being really good with Provinces and Colonies.
Defiled Shrine: I just love the interaction with Curses here. Curse is such a good card!