I can't really say I'm disappointed with this film, because I went in with Bay - level expectations and I got exactly that. The most frustrating thing is that there's good stuff in there, but it's buried below tonnes of ham-fisted emotional efforts and clumsy, chaotic action scenes.
The good stuff being the early parts of the film. The build-up of tension and mystery as unknown assailants prey on the military, and a new car exhibits some very odd behaviour. All of this is wiped off the screen once the central device (literally) of the story comes into play and the film barrels about from set-piece to set-piece - mostly without any logical reason (why for example do the Autobots waste time creeping around Sam's garden when the item they're after is so desperately vital? With giant robots rampaging all over the place do we really care whether or not Sam's parents see them?). Later on Sam is tasked with taking the Allspark to the roof of a building on foot - something any one of the Autobots could have done in seconds.
Performances are fine... Leboeuf in particular I was impressed with. John Turturro has fun with an atypical role, providing some decent comedy. The only weak spots come with a couple of the bit parts and Megan Fox, who is vapid beyond belief. I could have entirely lived without the secondary plot involving the soldiers from Qatar, but I suppose you have to throw a bone to the US military ego when you're borrowing their stuff.
I guess special mention should go to the Transformers themselves, which are realised completely convincingly. Unfortunately for them Bay's lack of flair with action reduces most of them to a blurry mess of metal shot from handheld close-up. Everything feels too tight and if anything really needs a sense of scale it's giant robots beating the crap out of each other. I never got that tingly feeling I wanted when Prime and Megatron were set to face off (indeed, that fight kind of fizzled to a close without me even realising at first).
All in all a passable dumb summer flick, but nothing special at all and amazingly quite boring in places.