The big problem I have with rockbox is that it eats battery life BAD (I have a 30 gig ipod video thingy) and it freezes and is generally slower than apple's default firmware. Basically now I just boot into it if I feel like playing some nsfs, the games are boring and spcs freeze it. ipods are really easy to reset when they freeze in apple's firmware (hold menu and ok for a few seconds) and I generally love the ipod and all of its features.
I also have a 30 gig zune (shut up I got it for free) and it SUCKS. The synchronization software always freezes midway forcing you to synchronize two or maybe three times to get everything you want on there. The lack of a scroll wheel may not sound like much but it is a BIG difference (scroll wheels are just so nice). So I'd advise to STAY AWAY from the zune, and because of personal happiness with ipods I'd say go with it.
Oh and my friend has done Best Buy's thing and he traded in his 3rd gen ipod for the 30 gig video. Basically you pay $30 and if a new one comes out or it breaks you get yourself a new one.