With the recent update i have noticed:
-Faster switching between home screens when multiple programs are running
-No lag or messing up when unlocking my phone
-Internet browsing is amazing, pages load in 1/2 the time
-New dialer menu
-Less force closes
There are some other minor fixes as well such as fixes to exchange sync, visual voicemail, and they added a new data widget which honestly i haven't tried out yet. Couple new apps are preloaded one being madden NFL, its actually a pretty cool game, however you can remove it via root with TitaniumBackup or Root Explorer if you would like.
Now this is important.
The biggest thing that helped me out as far as updating my phone was a post about a month or two ago on android central's article forum. (I will search to find the original post and update this)
i noticed that when i first upgraded to 2.2 i was not benefiting fully or getting all of the features. I have tried factory rebooting but it didn't work. Until, i read a post telling me to go into: Settings>Privacy> and uncheck "Back up my data" and "automatic restore" Then perform a factory reset. When your phone resets, skip adding your google account and manually do it after your phone is done with the tutorial. This ensures that froyo is properly running on your phone and fixes ALOT of phone issues. I have helped many of friends optimize their phone and have it run they way it was intended to. Because what actually happens is Froyo and now 2.2.1 is it gets installed but actually reinstalls your previous system data negating part of the update you received. If you want to ensure that the features of the updates work properly on your phone try this method and leave those two privacy options unchecked. Hopefully gingerbread will correct this problem in the future, but until then lets work around it.
-Masheen