I haven't tried any, but I've also not heard from anyone that used them and found them helpful. The same thing can be done without investing in a plate by visually portioning your food onto your plate, or by using a disposable plate with portions.
Portion size is important, but can be figured by using measuring cups. But also important is what you are measuring, and the plates don't really address that in any way other than a list of suggestions - which you don't need the plate to use.
I'd be interested in hearing from anyone that has used a diet plate