Running 2.1 (5F136) now, and here's what we're noticing: WiFi works fine (tried on Apple and Linksys routers). New icons for connection type (3G/Edge) in the top bar. New blue filled and half-filled dots to describe state of video and podcasts (watched/listened to). Genius Playlists don't seem to work as well as iTunes 8, at least for me, with lots of songs coming back as "not related".
We'll update this post as we discover more (sadly, doesn't look like cut/copy/paste to turn-by-turn this go around!). What have you found so far? Any surprises?
Screen cap gallery after the break!