There is another major advantage to the ipod - accessories...
It's not so easy to find cases, car adaptors, and docks for the creative or zune, ad certainly not the depth of choice you can get for the apple.
I've also said it many times on here, but you can't beat the ipod and bose sounddock combination. It's great quality, compact setup, and has almost completely replaced my stereo - the only thing it could do with is DAB, then it would be perfect!
Edit - I also travel a lot on business, so the selection of movies on the 80Gb video is really useful when you're waiting for a late plane!