My previous Littermaid box was over 4 years old and finally quit (it's used by 2 cats daily).  After checking reviews on the newer Littermaid models, I decided to stay with the LM500 and I don't regret it. The litter box size is a little smaller than the old box, but it works great (my cats each weigh about 7-3/4 lbs, they're small cats, so the size difference wasn't a major problem). I have no regrets getting this model again.  Sometimes I have to scrape the kitty goo from the bottom of the box where it seeps and coagulates, but I had to do that with the old box too. When you change and clean the litter box section, wipe some baby oil on the bottom of the pan before you add new litter, it helps to lift the coagulated kitty goo more easily.