Good point, but if you don't need to handle unstructured terrain, you might just as well put the robot on wheels. The humanoids robot Justin from DLR [1] for instance has an omnidirectional wheeled platform that even allows for adaptive foot print. The only current advantage for ASIMO that I see at the moment, is that it doesn't have to take the elevator but can use stairs.
[1] Here is a good video from 2009 that shows that Justin is capable of the same tasks that Honda showed of today http://www.youtube.com/watch?v=ZPwpGpMoAxs