My two16 year old cats have be using the CatGenie for well over a year now (60 tabby package). It took the cats a few days to figure everything out, but they love this litter box. I've tried every kind of litter, self-scooping litter box, etc. Recently, I had to have the pump replaced. The customer service was excellent and very helpful!
My male cat is about 2 foot long and 18 pounds, so it works even with bigger cats.