I agree outside of a handful of Transformers, the character design is questionable, but the actual effects are pretty incredible. There are also a handful of well executed action sequences that are pretty awesome.
Star Trek has the stronger cast, but I don't think anyone in Transformers is pretty bad. Strike that. Except Jon Voight.
I can't really recall a lot of character moments that involved a teenage boy getting a talking, robotic car for his Super Sweet 16 in many other summer blockbuster flicks. Unfortunately I agree with Cheebs, that when it is really a story about a boy and his car, it is pretty entertaining. It's only when it switches gears that it becomes purely a reference track for home theater systems.
... Any sequel to Star Trek needs a solid story, or this cast will go to waste. Someone also needs to let J.J. Abrams know that he's no longer shooting for television, he can actually pull the camera out. And the DP needs to be fired.