Never had one, and honestly I think they'd be a major hassle. Would probably be worth it if you were away and couldn't clean it for long periods of time. Like 24-48 hr shift job or something. But I'd read up on them thoroughly. Make sure the cat can't get stuck in the moving parts .

I had a litter maid years ago, it was junk and was more work, mess and germs than simply scooping out the poop twice a day and changing the litter every few days. Also buying all the items is very expensive and you can't use them without their expensive fecal receptacles. And if you wish to reuse the poop container you have to wash it of course. No savings of time, not any less messy (actually more messy ) and much more money. Oh and cleaning the automatic grate is a real mess, yuck! It's not worth it in any way.

Don't waste your money, just remove poop at least daily better twice daily and change the litter completely every few days.