In my humble opinion, it's a smart item only in a theory and ideal world.
The entrance is way too high for all cats. The entrance is roughly 10 inches from the ground, if not more, and I believe only big young and fit cats would be able to sneak in. Too high for a kitten or a small sized adult cat, too high for a senior cat or one with limited movement ability. For instance, I can't see my Freya go into it, she's so tiny.
The clumps are collected in the bottom drawer. I wonder if the box works better with a particular litter. In my experience, no matter what litter I use, some clumps tend to break when too big or even when they are regular sized but they decide to break, so I wonder what happens to those fragments of clumps that go through the "sieve". Would they stay in the litter?