I wouldn't update if I had it to do over on iPad 1. Safari and othe apps crash more often because of memory problems (as reflected in my iPad's diagnostics log). I also don't like the new Music app, and I don't use most of the iOS 5 / 5.0.1 features.
I see fewer memory crashes on my iPad 2, because it has twice as much memory, but Safari and other apps also crash with more frequency.
I did a backup and full restore with both iPads, as well as iPod touch 4 and iPhone 4, which I've since given to my husband, because I switched to 4S.