i've installed rockbox on my ipod, but it doesn't seem to be playing all that well with my 80G video model. while it's cool to be all open source (and be able to choose among themes and whatnot), i think i prefer working software. (hence my desire for a mac.)
the benefit is supposedly the ability to play ogg formats on the ipod, but i have no problem with mp3. i'll probably check back over time to see how the project is progressing.