I started a new world and played for a while. I noticed some of the new touches--yet more new chest sounds, the breaking of tools, the dripping water. Haven't noticed any actual changes to the game mechanics yet. I did notice shift-clicking doesn't move things to/from chests anymore.
Something else is that coal and iron are a lot
more common, from what I can tell.
Keep in mind I didn't really play the 1.9pre versions, so this is all new to me.