Whoops. I completely forgot about one of the earlier and most important changes -- the lowering of all shop prices, which actually made purchasing stuff a viable option.
Apart from that one, though, I've got to agree that the altars were one of the best additions. It introduced a bunch of new playstyles -- the Kapala and the ball and chain are fun new items that drastically change the way you approach the game, and the little "can I get to the altar before this mantrap/yeti/cultist wakes up in my hands?" metagame is a thrill -- and it's a satisfying way to obtain items.
Yeah that was a BIG thing. a lot bigger then most people know.
didn't it cost a million+ for a shotgun I heard such rummors.