This PetSafe Scoop Free Self-Cleaning Litter Box is really great.  First of all, this litter box is a hands free system that will do all the scooping for you.  It uses a crystal litter that absorbs urine and dries solid waste instantly all while removing odors.  It self cleans for weeks and the recommended tray replacement for a 1 cat household is 30 days.  All I had to do was load the unit, leave it for my cat, then change the tray after 1 month.  It is so simple and my cat loves it.   It is also a very quiet design.  In addition, it comes with cat acclimation tips if your cat is hesitant about using the litter box.  My cat had no problems at all!!!