I have to say I have toilet trained all 3 of mine - youngest being 13 weeks when she started.
It is great because there is no tracking of litter, they don't stand in their own wee or poo, if they have an upset tummy it goes straight down the loo so they dont stand in it when they turn round and try to cover it up.
I don't think it is cruel, cats like to be clean and it is helping them to have clean toilet habits.
The only thing I would love to teach them is to flush afterwards!!!!!