Do self-cleaning cat litter boxes really work?

I have two male cats and the cat box is gross. They pee a lot and I wonder if an auto-cleaning litter box would be able to clean up after them. If you have used one, please let me know how you like it and if your cats were OK with it.
Update: a little background info: I am mostly looking for something that I can leave on during the day and then just dump what has been pre-scooped when I get home from work. The cats are brothers so they have no problem sharing, but the last thing I want is for the box to scare them so they stop using it! Thank you for... show more a little background info: I am mostly looking for something that I can leave on during the day and then just dump what has been pre-scooped when I get home from work. The cats are brothers so they have no problem sharing, but the last thing I want is for the box to scare them so they stop using it! Thank you for the helpful comments.
9 answers 9