Another good feature of Roomba is that it can keep a group of engineers entertained for hours, much like a large format pen plotter!
Not very durable, though - we had one in the office (which admittedly is quite messy...) years ago and gave up after the third one broke. I would expect these new models to be improved at the weak points, though.
And yes, they would work best if there was nothing but hard floor. Furniture feet don't matter as long as the Roomba can get under there, but it will easily get stuck in anything rolling around on the floor.