No personal experience on this topic, but a few thoughts that might help you...
1. Do a search on the forums here for toilet training and see what comes up.
2. Go on amazon.com and read all of the "customer reviews" on similar products to those you mentioned... This seems to be one of those "if you're cat will do it great, but most won't" products. Also, there is a wide range in quality and safety in the products themselves.
3. Be prepared for the long-haul.... All of the threads and reviews I've read lead me to not go this route, because it can take a very long time, you generally do better if you have a spare bathroom (imagine having to move the tray w/ litter on/off the toilet everytime you go).
4. Be prepared to provide a regular box until your cat "gets it" otherwise he/she may resort to your rugs, carpet, bed, etc (and once those sorts of habits form, it can be very hard to break them).
I'd think that starting the cats on this early would be your best bet, maybe starting by training them to a very small round / oval shaped litter pan, decreasing the amount of litte, then putting it on increasingly raised boxes, etc...until it's at toilet height, then stepping up to the actual toilet seat cover device, etc. Apparently going very slow is the most common way to success with this product (from what I've read). This might also work best for a smaller cat...since it will have limited space to do it's business.
One thing that you should consider...using something like this will make it very hard to keep track of how often your cat goes (pee) and in what quantities, if it has blood in it, etc...so could make it harder to see signs of illness (like a UTI). the same could be said for non-clumping litter though.
I hope this helps, even if it isn't first-hand experience. Good luck whichever method you choose.