We have the Cat Genie - it's the kind with plastic pellets that actually get washed.
We are actually on our second one at this point - the first one started having problems after 3 - 4 years.
Is it worth it? Obviously to us it is, since we have had one for 6 - 7 years now!
The plusses
- litterbox is always clean, you don't get smell the way you can from a normal box (mostly... more about that in a minute),
- since it's always clean (cleans after each use), we have only one box for two cats (though we are in a single story condo; if we had multiple levels I would want one on each level)
- we never have to clean a litterbox (again, mostly...)
-when pellets end up elsewhere in the house, I can at least tell myself that they do get washed and sanitized, so it's probably better than litter that gets tracked
downsides:
- you have to buy cleaning cartridges and the plastic pellets, which can get somewhat expensive. It ends up costing more than a normal litterbox (though I think the convenience outweighs the extra cost).
- every so often, something solid will get missed during the scooping part of a cleaning cycle... which means that it gets washed, and then dried. This can result in a "baked poo" smell that is HORRIBLE! It has only happened to us a handful of times though.
- even though we don't have to scoop, the box does need maintenance. There is a cleaning cartridge for it which is a self-cleaning process. But there is a water sensor that must be taken out and cleaned periodically, and once in a while, a complete manual clean may be necessary. Still much better than scooping daily in my opinion, but YMMV.
- 2nd biggest problem: the frickin' water sensor. It's a bad design. It needs to be taken out and cleaned way too often (at least, in my opinion, though it's only difficult because we have the box in a location that makes it difficult to get to the sensor. If we had a better spot to put the box, this wouldn't be as much of an issue.) When the sensor needs cleaned, the freaking "three beeps from hell" mock you and about drive you out of your mind!
- And the worst thing: the stupid, fracking pellets get tracked everywhere. It is impossible to keep the cats from tracking them. So... you don't have to scoop the box, but you do have to vacuum up the pellets.
Overall, we find the cat genie to be worth it, but it's definitely personal opinion as to whether it's worth it or not.
Also - I had the littermaid before I had the cat genie. That one is a toss up as well. I eventually came to the conclusion on that one that scooping every day was better, because the smell when the thing scooped was bad, and there was no avoiding it. And with the number of cats you have, you'd have to empty the container at least every other day, if not every day, so I don't know that it would save you much work. And you'd go through a lot of disposable containers.
Oh, and we could never get the top part of the containers to stay on like they were supposed to, which added to the smell issue and sometimes meant that the stuff that got scooped ended up all over the place.
If I had the time and patience, I'd be tempted to try training the cats to use the toilet! I know it can be done.... but I don't have time to do it.