If I were a U2 fan who had shelled out for a "special edition U2 ipod" I would be kind of iritated that they continued to come out with more editions. Seems to reduce the speciallness.
Why not some other special edition ipods? The Rolling Stones are the obvious candidate. It'd be great to see a green Green Day iPod.
Then, once they've done a few of those, they can always release a pink breast cancer ipod.
Eh. The whole special edition thing has seemed silly from the begining to me. Lets just go back to white iPods, and add gapless, higherarical playlists, and a full running order editor.
Matthew