Drawn in by some of the very enthusiastic reviews I've seen, I bought one of these. I've had it for nearly a week, at the time of writing.
* it picks up a lot of stuff. Every time I let it clean up, it gets loads of dust and rubbish in its little bin. And that's with running it three times this week!
* it really is simple to use, and to schedule cleaning to begin when you're out
* it's not very tall at all: it easily fits under most furniture, and has a powerful enough motor to navigate over small obstacles
* it's persistent, and so visits most of the room - though not in a pattern you or I could predict!
* it doesn't leave the floor absolutely spotless. Maybe over time it will improve the general cleanliness of my carpets, and the number of little lumps of fluff etc. will decline.
* its location-awareness is kind-of weird: it tries to go around the walls/perimeter for a while, for example, but when it finds an obstacle its behaviour is hard to predict. So I really doubt that it gets into every corner every time.
* it really dislikes my Ikea Poang armchairs: a couple of times, it actually got stuck underneath them; other times it just takes ages to extract itself
* it rather easily tangles on cables (including the cable of its own base station): it will untangle itself, but that pulls the cables into weird places (and moves the base station around!)
I'm definitely glad I bought it, and I think it's going to make a real difference to my general cleanliness - not least because it will encourage me not to leave too much stuff on the floor. But those reviewers who say it's perfect must have incredibly uncluttered rooms, I'd say, and very little mess.