I have used iRobot 780 and Neato.
iRobot : Unreliable as it moves in a random fashion and cleans for a fixed period of time only. I had a walk in wardrope and it seldom goes into the walk in wardrope due to its layout
Neato : Finally sold away the irobot after 2 weeks and got the Neato. This one is smart as it maps the room before covering every part. Once it is done with the current room, it moves to the next, map and clean it. Moreover, if it runs out of battery, it returns to its charging station and once it is fully charged, it resumes from where it ended off before the charge. The down side is that it is super noisy. Sounds like a jet engine. But this is due to its more powerful vacuum. Anyway I on it when I am not at home.