Just like books, movies in general need to be scripted so that there is downtime in being spikes of action. It has been proven that the human brain functions best like that.
The reason I say that is because Transformers is 2.5 hours of non-stop action and mass destruction. It's too, too much without ever taking a break. I took my 5-y/o son to see it and felt a little awkward with all of the foul language used. Megan Fox is fine as can be, the special effects are jaw-dropping...but the movie needed to slow it down a notch. I left with a headache!
A lot of key things from the book were forfeited, some scenes that were in the movie did not occur in the book, and the whole storyline in general paid far too much focus on the wrong things (like raging teen hormones lol). There was far too much drama and much too little action, so the movie felt a little drawn-out at times.
The filmography and special effects were wonderful, the actors were good and there were indeed a few funny moments - however it just isn't true to the book, which is what fans ultimately want.