I've tried it on a couple of my cats and it worked well until the opening became about 4 inches around. At that point, both cats (done years apart) went on strike, started using the potted plants, etc. I think we might have gotten past it had I gone slower. I've heard it takes 4-6 months at least, to get a cat fully trained to use the toilet. Lots of info is on the net.

If you are simply sick of the mess of doing the box, or FORGET to do the box, like me, you might consider a Litter Robot www.litter-robot.com . It has worked very well for me for the last 3 years.

Good luck!