Great find! I was surprised to find how well the gui worked on relatively old mobile hardware. In addition, ubuntu with the rather heavy gnome has been seen running.

Debian on the G1:
http://www.youtube.com/watch?v=mjNhGjyAUAw

Ubuntu on the N1:
http://www.youtube.com/watch?v=3wQ9XogfjRU

Of course, for me (and you, I assume), this is more of a 'neat hack' than something that I would use regularly. While the notion of a debian computer in your pocket is enticing, the actual implementation is too awkward to be useful to me, and a laptop would be a far better device to use (or so my intuition tells me, anyway). Of course having a full traditional linux CLI in your pocket is INCREDIBLY useful (my N810 agrees with this), especially on such capable hardware.