They're somewhat less than speedy (most likely because they take a whole lot of breaks to argue vehemently over whose turn it is). They frequently leave the vacuum running unattended while they eat Cheerios and other less-savory items that they find on the floor (nice...). But they do eventually get to almost all the corners. And sometimes they dance or sing a funny little number while cleaning, which is something the brilliant marketing folks at Roomba just haven't quite delivered yet.
Note: I updated the Random Questions in the sidebar (at right). This time the questions were from Ani and GirlSpeaks.