3. Too many Chevy autobots. Nearly all autobots will be Chevys (except Prime). Why can't they throw in a better looking alternative mode here and there (I hate most GM designs).
While Ironhide is a GMC Topkick, Jazz a Pontiac Solstice and Ratchet is a Hummer (meaning only one Autobot is actually a Chevrolet model), I understand this gripe from a purely aesthetic standpoint ... but it's something that has to be taken with the realities of film production. Making the product placement deal with General Motors saved the first movie a significant amount of money, and that's totally forgivable.
Also, Ironhide's design was awesome and I will hear no argument to the contrary