I actually have two of these Littermaid Plus units and the cats really like them and have no problem using them. I, however, am not as impressed. There are markings in the pan for the depth you are supposed to be able to fill them to but they can not be used. The motor is not strong enough to do an adequate job of cleaning the pan so it frequently shuts itself down until it can be manually cleaned. Cleaning the teeth is a real pain and if you don't have their sifter that was specifically developed to fit in the teeth, it is a real mess. Because the price was so high, I really expected a better unit. Nevertheless, my cats do prefer these units because, if they are working, the litter is always clean and fresh. Especially if I happen to be out of town for a couple of days. They could vastly improve these units if the motor was a little more powerful and if they made the teeth just a little bit longer, too.