Few things i've noticed:
1) Lots more ram free for me. about 110mb more in fact.
2) moto blur weather widget now can use gps to lock your location so you don't have to put in a static city! I think it's the best weather widget and i have bought 2 different kinds and tried all the free ones. It seems to be the most accurate for me and i like how it gives me the 4 day forecast and 1 touch gives me the hourly spread during the day. I think it just beats out the google weather widget.
3) quadrant score increased by close to 100 pts
4) pin code lock screen has a new graphic
5) when you hold the home screen it's the last 8 apps, instead of the last 6
6) also, in 2.1 when i would go from the browser to a different app and hold down the home screen it would never show the browser as one of my last used apps. now it does and has been fixed
7) new battery manager including nighttime saver mode
8) battery status now show's EVERY app i've used. Before it only showed cell standby, display, wifi, and 1 other no matter how many apps i had used.
9) now in the Gmail app you can press a next and previous arrow so you don't have to press the hard back button to get to the list of emails. this is how the messaging app works. love it!
10) in settings > sound and display the menu choices have been cleaned up a lot
11) the moto blur news and facebook widgets now scale much better. in 2.1 the pictures would look jacked up and now they look normal.
12) camera app is MUCH faster! it is BLAZING compared to 2.1! it opens in 2-3 seconds instead of 5-6 and the time between shots has been drastically reduced. the time between shots feels more like the iphone 4 now.
will update if i discover more. lovin' 2.2!!!