I'm personally not a fan of toilet training cats. I say let cats be cats, and using a flushable toilet just ain't in their genetic code. It really only benefits the human in the equation, not the cat (unless the human is so totally lazy about scooping the litter box that it piles up to unsanitary levels and the cat doesn't WANT to use the box - in which case, a toilet would at least be better than that).
Also, most cats get arthritis later in life (80-90% over the age of 12), and using a toilet would not only be uncomfortable, but dangerous. It also makes it difficult to keep track of how much or how often a cat is urinating, which is an important aspect to monitoring their health.
Here's a previous post on this subject: http://www.pets.ca/forum/showthread.php?p=635013