I think it is best to ignore those that complain about these models being too fast, because obviously they don't understand basic physics. Just laugh at their comments, and let them have fun eating glue in the corner. Now I actually own a Scorpion set and for any coaster enthusiast these are the coolest things next to actually building a ride-able backyard coaster there is. It looks cool when it isn't running, but when it does run it's pretty sweet to watch the train travel around the track.
My main gripe is that some of the newer sets seem to be hinting that the company is moving more towards a toy-ish design, as opposed to a model style design. I'm sure the cheaper sets will sell better and keep the business going, which is good, I just hope their target audience doesn't completely change from model type people to spoiled kids just looking for an easy to set up coaster toy. It would be nice if the track pieces could be offered in various colors too. I'm lazy and don't want to have to mess around with painting them, and I would assume it would rub off somewhat easily anyway. I mean, it's just plastic, changing the color shouldn't be too hard or costly I would imagine.
Anyway, these models are pretty sweet! They are pricey, but there's nothing else like them out there. It would be cool if they could team up with No Limits so you could design a coaster in No Limits, then have the blueprints printed out to build with CoasterDynamix pieces. I doubt that'll happen, but I'm just saying it would be pretty cool to do so!