Even though I don’t personally have an iPhone, I have played with one and I have to admit, it is pretty fun. One thing I like are the various applications people have made for it. One that was really interesting, is Listen. When you have a song you are hearing, turn on your iPhone, put it near the music source and run the app. It will sample the music for a few seconds and then try to tell you the song, artist, and album. Its REALLY in beta, but its a wonderful idea.
Check it out: Ericasadun.com