I'm sat watching my Aunty's IRobot vaccum going about it's job in the living room. It's a nifty little thing, you just set up the 'walls' which tell it where not to go and whizzes about vacuuming the room while you go off and do other things. But I have to wonder how good a job it can actually do because it's very sporadic. Rather than doing lines back and forth say, it just goes here and there, round in circles acrosss one way, diagonal another.