If it matters, I would like to post my opinion:
I am the type of person who watched this movie just for the action. I don't really care that much about how elaborate the plot is, so I saw it twice. However, the movie has its positive and negative sides:
Positives:
-Robot fighting. SPOILERS: The scene where Optimus fights the 3 Decepticons in the forest is awesome, especially the part where he rips the helicopter one's face in half to kill it. The part where Optimus combines with Jetfire and takes on Megatron and The Fallen single-handedly was great too (if only Optimus did not disintegrate in the end).
-They had pretty big robots. I personally like seeing Transformers transform. SPOILERS: I thought the big guy at the beginning (the one without legs but moves with one wheel, dunno his name) is cool, but he does not get enough screen-time, which was a big disappointment. The big Megazord-like thing that sucks up all the sand is cool as well.
Negatives:
-The movie was too long. 2.5 hours is really long for a movie, at least in my opinion. Also, there is a huge gap of time between the two big fight scenes (they are mentioned in the positives section).
-There were a bunch of unnecessary humour. Some of them were mentioned: SPOILERS: dog humping, robot testes, robot humping Megan Fox's leg, Sam's mom high on eating marijuana, etc. I too thought they were unnecessary and I think it would have saved some time if they were taken out...
Yeah, if you like action, and action only, this is the movie for you. If you're going for plot quality and humour, I would not recommend it.