I've been installing iOS 5 since about 10 PM. The download went faster than expected (about 45 minutes).
Here are some of my notes.
After installing the OS, iTunes indicated that it was restoring my Apps however, I could see and interact with the iPhone.
Syncing is now a background task, allowing you to use your iPhone during the process. With that said, you probably shouldn't go messing around with app deletions and installations while this is happening. Bad Things may happen.
I hope it doesn't try to restore all my podcasts and audiobooks, since I'm moving to an iPhone 4S on Friday.
Oh - just got my first notifications on the lock screen. Very nice experience. See here:
And here's a notification while in an application (top of the screen).
Done. iTunes didn't try to sync my music, photos, podcasts or audiobooks which is good. I only sync'd my current audiobook and a little Coheed and Cambria, so I have something to listen to in the car. ;)
Total time: about 2 hours and 40 minutes.
Tomorrow: update the iPad 2 with iOS 5.