Any experiences with them? Good, bad, things to watch out for?
Is it a razor & blades thing where you’re gouged on the refills?
We had one for a while. We got it at PetSmart. I don’t remember the model. You do get gouged a bit on the refills and after a while those refills become harder to find for your specific model (at least ours did).
Ours did occasionally jam. We have multiple cats, and it did not hold up well to that much use.
The one we had would wait a bit after the cat was finished before doing its thing, to make sure that the cat was gone so it wouldn’t startle the cat and make them want to go somewhere else to do their business. If you get one, make sure it has this feature.
They are good for automatic scooping, but you still need to change the litter almost as frequently as a regular litter box. It didn’t feel like it was saving us that much effort. You save a bit of effort on daily scooping, but that’s about it.
ETA: Ours was this type:
The “last post” shortcut shortened the title to “Automatic/self-cleaning cat”. I thought: my cat is already self-cleaning.
I have a Litter Robot, but an older model. I recommend it; it’s been reliable and a genuine labor reduction. At some point, my cat got skittish about it, and I’m not sure why (maybe it went off when she was inside)–I had to set up a conventional box. I keep both around now and Nibbler seems to have gotten over whatever she didn’t like about it.
At any rate, the Litter Robots are expensive but work well. I’m sorta curious how well the new ones work. There are no “razor blades” required; I used ordinary trash bags for the waste tray, and there’s nothing else disposable about it.
We had one years ago, and our cat was fascinated with it… We used to hear “whir, whir, BANG, BANG”…
Turned out every time the little rake was doing it’s job, the cat was trying to attack it… He did that for years…
But, it entertained him, (and us!), so it was worth it
I used one for more than a decade. It was nice to be able to glance in the room and note that the litter was clean and didn’t need my attention. Once or twice a week I had to change the “tray” and maybe once or twice a week I’d have to do some scooping’ myself, but overall I found it worthwhile.
I finally got tired of the litter tracking tho and I’ve been using the Breeze system since it was introduced in the US. Yes, I have to scoop it myself but I don’t have cat litter all over my house anymore. Priorities, eh.
I want one really bad. My 2 would revolt, I fear. They are really nit-picky about everything. So I don’t dare. My male uses the toilet occasionally. Which is real fun, I tell you. He’s a genius in his own mind. 
To expand in this: we’ve been using the Breeze system for a couple of years, it’s great. However, the pellets are a rip-off. We started out by using plastic BBs, which can be washed and reused. They worked well enough, but they get kicked out of the box easily, or stuck in paws, and I’d find them all over the house (we have all wood floors, so they’d roll all over the place). Then, about a year ago, I saw a suggestion online to use pinto beans. It works great. The beans are too heavy to get kicked out of the litter box much, I only have to pick up a few around the box each day. They do start to get a bit rank after a while, so about once a month I have to toss the entire batch and replace it. But a 25 pound bag costs like $15 at Costco, which lasts about six months for two litter boxes.
I could hire migrant Lithuanians to clean the cat box for $450.00!