Actually, CoverFlow is nice.
I'm going to double back on what I said yesterday about CoverFlow's usefullness on an older G4. Yesterday evening my wife spent about an hour flipping through our movies folder watching old videos, and she loved it. It really is a great way to browse through pictures and movies, with the only drawback being that on a G4 it's going to need a bit longer to load up all the icons. That being said, I still don't know if I'd recommend upgrading if your only machine is an iBook, unless you are going to use Time Machine. If you've got an external disk, and aren't using it regularly for backups, but you would if you got Leopard, do yourself a favor and upgrade.