For those out there who find the 100 song cap (amongst other things) on iTunes phone a deal breaker, Engadget Mobile might have found your saving grace. A forum at MotoModders has the details and simple steps you can take to run a simple hack on any iTunes phone (except the v3i) to raise the song cap to 1000. Unfortunately, there's one catch: the little app you have to run is Windows-based, so you'll need a PC or Boot Camp to actually do this (sorry, Parallels doesn't support USB devices - yet).
Obviously this is a hack, so don't blame us or MotoModders if something goes wrong. However, if you do try this, please post your thoughts and let us know if it really works.