For what it's worth, one of my friends trained her older, rescue cat to use the toilet over the course of about six weeks. They used the Citkitty system too. Now Mike is pretty good about it. He will still go in their closet if they leave the door open, but that's because he got in there one day and decided it was a fantastic place to go. Now they keep the door to their room closet shut all the time.
Of course, they've had to deal with some side effects. For instance, no more bathroom reading. Also, they need to leave the door cracked during their showers, and long soaks in the tub with the door closed are a thing of the past. They say it's worth it to not have to clean up litter boxes.
Since I have five cats, two of which are boys, I've resigned myself to having multiple litter boxes to clean. (We have four boxes.) I just can't see the system working for that many cats, and I'd rather rescue more animals and deal with the boxes than have fewer pets and try to make them use the toilet. I know others' mileage will vary!
Also, they need to leave the door cracked during their showers, and long soaks in the tub with the door closed are a thing of the past. They say it's worth it to not have to clean up litter boxes. 
