Though it'd be cool, I don't have much use for a headless iMac, or for the "iPod shuffle." I'm more looking forward to the word processor app, believe it or not, as long as it's up to the same high quality as Safari and iTunes.
But the one thing I think they should do with the headless iMac is give it some sort of Tivo capability. All the components are alreay there, and all it needs is a tv tuner and some sweet assed Apple software for managing your TV shows. I have my doubts that'll happen, but it'd be cool.