The Graco "rewards potty" is going in the can! I posted earlier before about areas that my son peed into that went undetected - ick.
So I went and picked up the Baby Bjorn Toilet Trainer- and it it awesome! The seat stays firmly on the toilet, so when he climbs up onto it doesn't scoot around - giving him a sense of stability.
Also, the seat is one molded piece, so there are no cracks for pee to become trapped in.
The pee guard does not seem to bother him at all, whereas the detachable one on the Graco potty made him frustrated.
Last but not least, the toilet trainer has a picture of a bear on it. So it's his new "bear potty" and he is loving it!

If you are trying to switch from little potty to big - this is an awesome seat.
Only thing is that this application is probably best if they have their own bathroom. It is easy on and off, but you do have to adjust it to fit your toilet when you put it on.
:-) Potty training is good again!