I used to have an automatic litterbox and it was loud and seemed to run all of the time.  This scoop free classic self-cleaning litterbox is quiet (except the cats scratching on the crystal litter).  I have one cat that likes the crystal litter and 3 that don't. I read up on a tray that's not disposable and litter that works with the scoop free litter box and my cats like that much more.  I like that I can replace just the litter and it's not quite so expensive and all my cats use it.