I'm not rooted and just updated to 2.2.
***WARNING***
The Alarm app is gone, replaced by an app called Clock. My previous alarms are gone. Anyone who relies on the phone's alarm to wake-up will need to reprogram alarms.
Otherwise, this build feels great. Just starting to check out new features now.
There are a number of new apps:
Voice Recorder
Video Player
Task Manager (same as 2.1, but now in App List)
News & Weather
Free HD Game
Clock (Alarm app is gone)
The Calendar app has a new icon, which I like a lot better considering the old icon displayed 25, which was not the actual date. Wish the actual date would display like iOS and webOS.
The messaging app now color-codes sent and received messages.
Touchwiz 3.0 allows more customization of home screens. The four "quick launch" icons remain the same and can't be customized. (Wrong: they can be customized)
Skype finally works!!!
I've moved some larger apps to the SD Card, which is great.
I'd definitely be interested in updating to the official version of 2.2 that moves OTA, but I'm not sure if that's even necessary at this point.
I'd love to know if the "Airplane Mode Trick" is still required to stop the phone from searching for a GSM signal.
GPS seems to be more responsive, but I wasn't really having problems getting a lock with 2.1.