I have two cats - brother & sister. Puss likes to pile up the front with litter and then do her business. Boots likes the back and demolishes her "hills" (thank goodness). Boots LOVES this litterbox because, being a big cat, he now has the room to maneuver and poop - and poop he does! First time out he was in there for quite a while and left a nice pile of poop. With the other litterbox he was in an out and sometime had problems going. Now he takes his time and is much more regular - a good thing for a male cat. The litterbox is tall and long which he loves even though it's not as wide as the old one. I don't bother with the door on because they wouldn't step in there if I did. Even so, we have no problems with smells (except initially when they're pooping, of course). Am definitely getting another one for upstairs.