Exchange support works as smoothly as Scott and Mike had hoped, but there's still no two-pane Mail client. The multiple mail message selection works, however, and we finally found out why the Calculator button has changed -- apparently there are a ton of new features in there, including a sideways scientific calcalculator. There are a number of other fun features and improvements as well, although the main event, the App Store, only functions enough to give an error that it can't connect.
June can't come any faster, as far as we're concerned. Bring on the iPhone version 2.0!
Gallery: iPhone firmware 2.0 hands-on