I confirm this. Just did it today.
Had 10.0.4 on its own partition - nothing except apple software on it.
Reformatted and installed from the 10.1 upgrade cd. Voila! Lovin' it!
I would be glad to mirror a few people at a time if someone would teach me how to do it. Probably not worth the time though, since there are other people and I'm in England.