I have nothing nice to say about self-cleaning litterboxes.
I bought one of the LitterMaids for my girlfriend a little while back, and we soon encountered several problems:
First, when it runs, it's pretty loud.
Second, unless you have just the exactly right amount of litter in the box, when the little rake piece sweeps back across the box after scooping the poop, the excess litter will fool the box into thinking that there's a cat in the way. When this happens, the rake will reverse directions, and will inevitably end up raking back and forth across the box, over and over again, until someone goes over to it and scoops out the excess litter. Some days this would go on for several hours.
Third, the cat was fascinated with the mechanized rake, and would poop over and over again just to watch the litter box clean itself.
Fourth, it stinks. Badly. Between raking through the litter, and dropping the dropping into a pile of old droppings, the machine created a world of bad smells. We could actually tell whenever the cat had done his business, because the whole house would suddenly smell quite foul. I wish I was exagerating, but I'm not.
So... the litter box is now stuck up in an attic somewhere, hopefully never to be used again. We've gone back to a regular litter box, and are quite happy with it now.
(side note: I bought my gf the litter box, and in return she bought me a Surefire E2e. Guess who won out in that deal? Hehe...)