Life-changing
My fastidious 6kg ragdoll hates to encounter his previous "deposits" and used to cry for me to clean his litter tray every single time he used it - day or night! If I went out, rather than go in a dirty tray or - heaven forfend! - soil the floor, he would hold it until I got back and could clean out the litter.
This tray is so big that he is happy to use it more than once as he has room to go without getting too close to evidence of his previous visits. Life-changing for both of us!
The door is detachable, and as my raggie is not a cat-flap user, I left the flap off completely for the first few months while he got used to having a box rather than an open tray.
As other reviewers have pointed out, the box is not at all air-tight and there is a large gap around the door. My cat found this very useful when he was getting the hang of the door, as he could put his paw through the gap and try to get some purchase on the door that way. The filter in the lid does not absorb all smells, but it does help. Combined with a good litter and regular cleaning, the box is almost smell-free.
Another reviewer rightly points out that the box is significantly smaller at the base than it is six inches up. I find this quite useful as it means that the base can be completely covered with a relatively small amount of litter (convenient if you are running out). On the other hand, if I know I won't scoop out the box for a day or so, I can put in most of a bag of litter and fill it up to the height where the box is broadest, to give my fussy boy the maximum area.