1. Multi-tasking: Nope
2. Folders: Check - works as advertised
3. Unified Email: Check - works as advertised
4. iBooks: Didn't test it
5. Enterprise Feature: Check
6. Game Center: Check
7. iAds: Check - not tested (should work, though)
Another thing I noticed, setting up a wallpaper (under Settings) for the home screen (not lock screen) does not work on 3G.
Did you try to restart your phone? Others were having problems too, but it apparently works on the 3G. Even though I will be getting the new phone, I still hope it works on my 3G too.