I bought one of these based on reviews and whilst i was skeptical i was quite excited by the prospect of something to help me with the house work.
The first few days I must say i was disappointed. It didn't do a very thorough clean and felt I'd wasted my money.
However, I've now had it for about a month and slowly slowly it has become my "cleaning companion". If you think of the old roller carpet cleaners that surface cleaned carpets and swept hard floors, I would say Roomba does a similar quality clean. However, realising it does it itself and you don't have to lift a finger it's actually great. I now set it to come on while I'm out to clean a couple of rooms and when I come back it's much better than when I left. I also realise that if you watch it work you see everything it misses, but if you leave the room and come back later the room is clean, so it does cover most of the room. Just don't watch it, it will drive you crazy.
Something it does which my vacuum cleaner can't is clean under the beds, it's also quite good with cat fur and hair.
You still need to use a normal vacuum cleaner to get a deeper clean BUT Roomba makes the house nice in between. It's definitely reduced my stress of housework and being a working mum time is something I don't have much of.
Would I recommend it? Yes, definitely, but don't expect it to replace your vacuum cleaner.