The main reason I wanted to see this film was because of the cool special effects that the first one had. I wasn't disappointed in that regard, but I was with the excessive sexual humor and language in the film.
The one thing that keeps me from giving this movie a 2 is the moral character portrayed by some of the transformers (primarily Optimus Prime). It's rather ironic that he is portrayed as a higher level of being than the humans in the film. The humans are portrayed as more immoral and careless/carefree, not really comprehending right and wrong. With exception to Sam and his overly accentuated girlfriend, the humans are just the side-show. I know that it's supposed to be that way, being called "Transformers...", but the irony comes in the fact that the robots showed better moral judgement than the humans.
The film really over did it with all the slow-motion seductive cuts of Megan Fox. Though talking with most people I'm in contact with, the one thing they remember from the first show is "the girl in the transformers is hot," so I'm sure that's just an extra audience Dreamworks was trying to win back.
It seems that in the end, the real battle between good and evil is reserved for the Transformers. While the film did a decent job showing Sam's moral development in trying to overcome his adolescent selfishness exhibited in most of the movie, it wasn't enough to make it worth watching.
It was a semi-fun thrill ride with plenty of action and cool effects, but I wouldn't see it again, and I don't think I'd recommend anyone spend the money on it. Go see Up instead.