So far:
The entire notifications bar has reworked icons.
There's now a "Downloads" app, or I didn't notice it before.
Apps menu in Sense stays open when you hit back from being in an app. Is that new?
The phone seems snappier but might be due to phone reboot and excitement.
Zeam Launcher now runs a little laggy.
Edit:
Pressing and holding power button now only gives three options: Power off, Airplane mode and Restart.
This makes me sad. I want my Silent/Vibrate options back!
Pressing power button and then pressing it again to light up screen now has a fade in for lighting up. Kinda neat, possibly annoying.
Managing Applications app now has a reworked interface. Shows RAM and storage usage at the bottom.