I just upgraded both my iphone and iPad 2 to iOS 5. I love the changes!
A few tips: Leave yourself plenty of time for the download and update. Also, make sure your device is completely charged. It takes awhile to complete the update.
So far I like the changes. iCloud seems to work great. I turned on iCloud for photos, so anything I take on both my iphone and iPad 2 will be shared. No more syncing with itunes or emailing them to my other devices.
The biggest improvement is the ability to project wirelessly to my AppleTV. This changes everything for me when it comes to projecting in the classroom. Now I need to convince my department to purchase one for classroom use.
Here is a video that I shot at home with the wireless mirroring at work using the National Geographic 50 greatest photos App.
Good luck on the upgrade!