I really went into this film with pretty low expectations, I don't necessarily like Michael Bay and the last movie Steven Spielberg was involved with that was actually worthwhile was Jurassic Park IMHO.
I also can't say the trailers impressed me nor did the idea of the show focusing on the humans sit with me too well (Seriously, if we didn't have to deal with those damn meddling kids, half of those anime adaptions of the series would have been cool. That and humanizing the Autobots:rolleyes2 )

With that said, I was completely blown away by the film. I was quite surprised. Sure I would have loved to see some more of the Decepticons and Autobots like Dreddz and Vivi22 mentioned, I still feel it did a pretty good job. I also laughed quite a bit (especially the mother asking her son if he was masturbating and the scene where Bumblebee tries to hook the two humans up, his choice of musical cues were priceless) and this coming from someone who most people consider not having a sense of humor. Overall, considering the people behind the flick and the fan expectations, not to mention the usually bad quality of adaptions by Hollywood, I would say it came off way better than expected. Though it really did feel like ID4 at times, it was quite good. Definetly the best movie I've seen this year and the first summer blockuster flick that I felt was actually good. (Curse you Spider man 3 and Pirates 3! )