I was interested in doing this as i've gotten too used to playing games with xbox pad and xbox games are rediculously overpriced!
However many new games (Arkham Asylum, for example, which is a good game btw) on the PC can be played with an xbox pad, which is what I do. Having good gaming rig and usenet, I now have no use for my xbox as I just play them on my PC... Which reminds me I must stop paying for xbox live.
I do however buy PC games which I wish to play online with (I've bought CoD:WaW for both Xbox and PC!)