Can I backup iTunes 9 before upgrading to iTunes 10?

I am happy with iTunes 9 and am a bit leery of upgrading to iTunes 10 on my Mac based on some feedback I've heard from others. Can I duplicate iTunes.app in my Applications folder prior to running Software Update to update to iTunes 10, and use the backup iTunes to run iTunes 9 if I am not happy with iTunes 10? I know this works with some applications like Final Cut Pro but not with others like Safari.

Don't see why not. If you're paranoid, you may also want to backup the iTunes prefs (~/Library/com.apple.itunes*), and/or any config files you find in your iTunes music folder (~/Music/iTunes/ in my case).