I have one since getting my two kittens last October. I liked the fact that it has very high sides, a side door (as you mentioned), and open top (no cover) so I can always keep an eye on how much is used and scoop it often as needed. Both my kitties use it, but for kitties to turn sideways, it will have to be a full grown cat or one that you expect to be on the larger end of the spectrum, like Maine coons or Ragdolls, for example. They have much more color selection now, so that's also a nice feature. When I got mine, they only had the dark greyish one and white.
Earlier this year, I've added a second litter box, but this time using a Sterilite clear storage container (56 quart size) for about $7 at Home Depot. Actually, this one has been the preferred box out of the two (going by its frequent use). It seems the larger box you can have, all the more attractive for the cats to use.
Hope this helps!