Holy cat hair, Batman! We've only got one cat, but just running the Roomba in the kitchen was enough to pick up more cat hair than I thought was possible to have in a kitchen (without huge visible clump, of course).

I do have a problem in one room that has pretty deep pile carpeting. The Roomba does fine on that, but once it hits the rug that's on top of that, it just kind of sits there spinning its wheels.

I had another problem when my son dumped a half a box of Lucky Charms on the kitchen floor. Rather than pick it up, I just put the Roomba on it. When i came back a few minutes later, Roomba was making a horrible sound and smelling bad. I picked it up and saw that there were a couple of pieces of cereal that were large enough to get lodged above the beater bar without making it all the way in to the bin. The repeated spinning of the beater bar had actually worn/burned the rubber on the beater bar. I thought it was weird that the Roomba started to disintegrate before the cereal, but that's due to the magical deliciousness, I guess.

Other than that, the problems I have aren't Roomba's but mine, such as having a nasty habit of leaving way too much crap on the floor instead of putting it away.