The robot vacuum cleaner technology is a lot like a dancing dog, in that you are spending so much time being amazed that the dog can dance at all that you fail to notice what a horrible job it does of it.

Never used one personally but that quote stuck out in my mind

And that's exactly what's wrong with it. It looks like it's sweeping the floor, then you see the dust bunnies in a few days and realize it's just pushing the dirt around.