Excellent with minor drawbacks
It's brilliant for tracking. The only issues are that cats often wee in the gaps so makes it tricky to clean, and odour control isn't the best.
This is a good idea to keep litter and smells contained to a degree, but if your cat is quote big they might not like it. My cats are quite big and they weren't sure at first, but after a while they used it. I have a few different boxes so they have a choice and they do seem to prefer the one without a cover. It is a very large box so also be sure you have the room.
We bought the grey box as a first grown-up box for our kitten and our older cat took to it immediately! I have removed the swing door so cannot comment on any problems that may have. The only thing we have found is that the scoop is rather small and tends to fall off its hook so we dont use it! For this reason I have droped it a point tho it is a bit harsh as the cats, yes even the kitten, are quite happy to use it and I find they dont seem to manage to lose as much litter over the floor as their other box does. All round great box of good size for even our large cat.