I've had a little robot 3 for 5 years. It isn't the most reliable device in the world, but you learn very quickly all the little quirks of how to fix it when it breaks and it isn't too bad. I'm very, very happy with it. If you aren't handy then it might be more annoying for you.

My only complaints seemingly are fixed by the litter robot 4: better sensors (so it breaks less) and a larger poop storage. I would buy one immediately if I didn't already own the LR3.