Gentlemen - it is good.
Not Donnie Darko, Fight Club or Heat good, but good enough for an event movie, and all that that entails - explosions, fast edits and kinetic action. The dialogue is on occasion quite ropey, but mostly it knows that any movie involving giant robots fighting over something called "The All-Spark" - especially giant robots named things like Bumblebee, Ironhide, Starscream, Ratchet and Megatron (that's just a sampling, folks) - is going to be fighting a losing battle when it comes to credibility and suspension of disbelief. They make the movie work by (generally) not taking themselves too seriously.
Funnily enough it's the humans that get the best exposure - Shia LaBeouf and Megan Fox do pretty well as the human leads, and the supporting cast is uniformly good as well - except for the NSA analyst/hacker subplot, which is quite frankly a waste of good space.
But in the end it's the robots whose characters are not developed enough - when one of the autobots die at the end it's kind of hard to care, which is a little unfortunate. But they leave the door wide-open (in a non-groan-worthy way - stay for the credits, folks) for a sequel, so maybe that will be an chance to flesh everyone out a little: cf X-Men 2 - and hopefully not X-men 3.