I keep seeing those ads about the floor vacuum that does it all by itself. I think they are called Rumba or Roomba. I know we have all seen the kitty cat riding on one. But I've never known anyone that I could ask about them. Have any of you bought one, or know anyone that has? I can keep this big old place clean, but sweeping or vacuuming kill my back, so I was wondering if one of these little machines would work for me. I afraid to ask what they may cost. So, have any of you got any opinions on these little contraptions?