If we're going to be real, okay (spoiler alert): the movie was TOO long. They dragged that dessert scene for ages, which they didn't need to because the story is formulaic, we know Optimas Prime is going to be resurrected and he's going to kick ass, so dragging it on just made everything a bit too melodramatic. The storyline was sloppy--it had a lot of potential but they tried to complicate things, there was a lot of disorganization, rushing through the actual meat of the story. It confused me. That was the beauty of the first movie. They kept it simple and concise and it worked out because they let the characters and the action do the work. We didn't have to try to figure what was going on while we watched cars and robots crash into each other (deciphering plots is difficult to do when there's so much sensory overload). And I have to agree, although the special effects were incredible, I often found myself questioning whether that was an Autobot I was seeing or a Decepticon. It didn't help that they merged Optimas Prime and a Decepticon (although that was VERY cool). The characters seemed more 2D than usual, but it didn't bother me.
All that aside, I still really liked the movie (the first was way better though). I liked what they did bring to the table, the material was good enough (the ending fell a little short, but I was sort of expecting that). I loved the humor in it, it was so alpha and beta male style--I can see how some people might be turned off by that, but come on. They're trying to please a demographic here (cars+robots+hot girls... gotta have that kind of humor interplay). Bumblebee was awesome. I wasn't expecting Isabelle, but sure, I'll buy it.
If this kind of movie reaches out to you, you'll probably have a good time. I think you kind of have to be into the alien robots, cars, that macho-guy sense of humor, massive action scenes or at least be open to it to like the film. By the way, Optimas Prime stole the show every time he came out. He has the best entrances ever.