I'll weigh in some of my notices: (I only have iOS5 installed on the iPhone 3Gs 32GB, as of this post)
- Netflix doesn't work.
- During Sync, the phone slows to a crawl. The good part, you can still use the phone while it syncs.
- Notifications work for Facebook & Twitter, also with Phone, Words with Friends, etc.
- Facebook works fine. At least for me.
- Newsstand has no Magazines and the "Store" is greyed out.
- I have iCloud set up with Lion DP4. It syncs all my Contacts, Calendar and other information perfectly. I make one change on the computer, it shows up on the iPhone and vise versa.
- The iCloud Back Up seems to be broken. It took 1.1GB for my iPhone back up but it never completed even after leaving it overnight.
- I don't have anyone with iMessage to test. (Anyone wanna give it a try? Lol)
- Radio applications I use daily include: ooTunes & DI Radio & Pandora. All seems to work without any issues.
- Camera's photo roll count doesn't update when I save a photo from MMS or taken a photo from Camera. Restarting the Photos app fixes that.
- Beejive works fine. I do get AIM disconnects but I had that issue under iOS4 as well.
- Under iOS4 and iOS3, when you activate the EQ under iPod (Music now), the volume is decreased. That seems to be fixed now.
Just to list a few...