Roomba -- robot vacuum or remote control frizbee?

Does the Roomba actually work? I mean, it looks like a cute gadget, but will it actually do what its promoters promise? Can I plug it in, just let it do its thing and have a clean floor? I have a dog, and I am worried that he might think it is a toy and try to chew on it. The thing does look like a low flying frizbee. In that informercial they have a woman kicking back when her Roomba sucks all the dirt off her floor, but I think it makes more sense for a single guy to have one of these, why clean when you can have a machine do it for you? That's if the Roomba actually does work and I could keep the dog away :-).

If I had the time it would be fun to make my own robot vacuum, get a used laptop and some robot controller hardware and see what I come up with.