We bought one when we had the dog, to keep him from snacking on the litter, and we like it pretty well. IMO, its major advantage (for us) is that it makes cleaning the litterbox easier (no more looking for a bag and tromping outside to the garbage can with it), so the box gets cleaned far more often. Assumpta's not a real smelly cat, so I can't say it contains tough odors like a dream, but it certainly has been capable of containing her minimal odor in a pretty small room.
We don't turn the drum more than once a day, usually when we scoop the poop (we use World's Best Litter, which is corn-based and clumps well), and haven't had any trouble with smells (and I think a big part of this is the litter). Changing the bag/emptying is pretty easy once you figure it out. If you have multiple litterbox locations, it would probably be a pain to haul it around (it does get heavy as it fills up), I had planned to keep a coffee can at the upstairs box and carry THAT down to the locker, but Assumpta has never been interested in using the second box.
The biggest drawback I see is the expense of the bag cartridges, and that they don't seem (so far) to last quite as long as advertised...but other than that, we like it because it means a cleaner litterbox and less bags.