Nothing positive yet. (I'm not negative by nature, but gotta call it like I see it.) Hopefully I'll find some.
Downsides so far:
1. If anything, decrease in speed. OS dogs.
2. New car screen loses Maps button. You have to scroll to next page to get maps. This is the one function I used every time in my car. FAIL!
3. Helix Launcher (which I've loved as a great improvement over the native launcher) NOW CRASHES every time I hit the Home button. FAIL!
But this is the responsibility of HL authors. Hopefully they'll come up with a fix soon! Pleeeeez!
Give the update time. If after a couple of hours and a reboot or two it's still laggy as heck, the only option is to install the larger update file manually. It will clear your lag issues right up.
The maps thing sounds like a problem. Maybe there's a setting you could change or an app you could run to fix it.
Helix Launcher doesn't like FroYo. Why the Dev hasn't updated it considering the Android 2.2 SDK has been available for months is beyond me, but it's possible s/he/they don't care. Try ADW or Launcher Pro as already suggested.