The actors are fine. Batman Begins being the exception, no one really goes to summer blockbusters expecting stellar acting. Shia Le Bouf is convincing as a nerdy kid with charm, while the hotness that is Megan Fox succeeds at being sexy while not being purely eye candy. Props to John Turturro as head of Sector 7 for providing the right amount of ham this side of William Shatner.
Production design is stunning; the robots actually look alien and believable as mechanical warriors. The only real complaint is that, aside from Prime, Bumblebee, and the hacker Decepticon (who had a lot of screentime), the robots can't be told apart in a fight scene.
And boy those fight scenes were fantastic. The Transformers have their own martial art (bot-fu?) that looks like it's based on momentum. Ironhide, for example, would drive fast, jump and transform in mid-air, and execute parkour-type moves while hitting the enemy. Starscream taking out an F-22 squadron alone is worth the price of admission.
But while the action should be over the top, small, character moments need to be handled with a bit more restraint; something that Bay needs to invest in. The small moments are punctuated by an annoying score that is just a shade better than a laugh track. It redeems itself, though, with the faint strains of the Transformers G1 theme that you barely notice.
Writing is where this film fails, although I'm not placing the blame squarely on Kurtzman and Orci's shoulders. Big-budget blockbuster scripts are hacked by script doctors mercilessly (just look at the sorry mess that was “Gladiator”) to accommodate scenes and actors and lines.
The idea of placing Spike at the center of the story is a good decision, giving the film a relatable main character (with a hero's journey) to hook the story on. And while the part where Bumblebee “befriends” him is a tad too long/slow (bring on the fighting robots, Bay), the courtship scene aided by an intelligent car radio saves it from being too mundane. (That and the bug's car freshener)
The film missed a great opportunity, though, by not including a scene where the soldiers (Lennox's Spec Ops team and Prime's Autobots) bond. Comrades-in-arms makes for a decent plotline and will have given the other bots more screen time. It was practically set up already as the Autobots here were not the large-ish army of the cartoon but a small infiltration squad, much like Josh Duhamel's team. The hacker subplot could've been done away with to little detriment to accommodate this. But I'll take what I can.
As with any summer film, there are scenes to watch out for. Keep your eyes peeled for Bumblebee dissing a VW Beetle, a squad of Autobots hiding in Spike's front lawn, Prime commanding them to “roll out,” and “One shall stand, one shall fall” among others.