So, I installed iOS 5 yesterday. Very easy to do. Remember, you need iTunes 10.5 Beta 7 or higher to do this. Restored everything from my backup as I hoped.
I love the new notification system, where it drops a small title bar down from the top of the screen. I also like how it shows notifications you've missed on your lock screen, a cue taken from what jailbreakers have had with intelliscreen and LockInfo for a few years now.
You can finally create your own albums, which is essentially like tagging your photos, much like how you label messages if you use GMail. This can prove to be useful, especially if you have 100s to 1000s of photos in your Camera Roll.
I haven't had a chance to use iMessage, as I don't have anyone's cell # with iOS 5 already installed. Also, not sure how the iCloud is working out yet. I haven't enabled it to sync photos, but it is syncing contacts, calendar, reminders, and bookmarks. You get 5GB of storage to use with up to 10 devices. 5GB can get eaten up quickly, so they sell 10GB, 20GB, and 50GB yearly plans, for storage.
I really liked how it gave me the ability to install apps I had purchased already but weren't installed on the phone. That, my dear, is excellent.
I like how you can select a word and choose Define, and it'll bring up a dictionary entry for the word.
I haven't tried Wi-Fi sync, but am looking forward to that. It supposedly will sync with iTunes on my computer when the phone is plugged in to power and connected to Wi-Fi. Update: Doing it now. Hang on to your hats, kids! I pushed Sync Now. It was syncing, so I thought. Nothing happened. I can press Sync Now again,and, it says that my last sync was yesterday at 6:35PM.