1. Better Exchange Support
2. The Ability to use a Numerical Pin to unlock the phone instead of a Swype Lock
3. Adobe Flash 10.1
4. The Ability to install Applications to SD Card
5. Push Notifications (C2DM)
6. More GPS Fixes
7. Performance Increases
8. User Interface Enhancements (Set Default Home Screen, Expose-like Pinch Zoom-Out, etc.)
9. Fixes to decrease the amount of lag due to RFS
10. Faster Browser JavaScript performance
11. The ability to run applications that require Android 2.2 - The List is growing
12. Better radio in the update will result in better signal quality and data speeds
There is more.
The way Android is handled IRT updates and such is a huge fail and IMO is a reason to stay away from those phones.