It looks like the big feature is taverns, poetry, and music. This looks like its more an atmospheric change to make DF feel like more of a real world, but doesn't really change gameplay alot. Is that correct?
I can only really speak to Adventure Mode since that is what I play lately...
-- NPC's seem generally a bit less cowardly now as compared to .40, which I assume comes from the revamped personality/needs system?
-- Depending on your play style, the new personality/needs stuff has a pretty big impact in Adventure Mode with much more dynamic conversation options, including the ability to argue with NPC's and change their minds about things, or have them change your adventurer's mind. As it exists now I'm pretty sure Dwarf Fortress Adventure Mode has the most dynamic, robust, NPC interactions of any game ever, and its all organic stuff and not scripted.
-- the new Taverns add a lot of atmosphere to Towns, and places to get into drunken brawls and use the new performance stuff, etc. So far Temples seems pretty much the same to me but maybe I'm just not noticing the difference
-- The performance stuff is mostly just silly fun and adds background atmosphere to Towns and such...but it does also open a whole new play style within Adventure Mode.
All in all its baby steps, but more important foundation stuff being laid down. Adventure Mode is now a few bug fixes and new features away from being something really incredible. The World Activation from .40 and the revamped Personality/Needs stuff in .42 are two MAJOR steps forward in the quest towards DF becoming a true Fantasy World Simulator.