What let the film down in my opinion was the length and the storyline of it. There were so many scenes, including the ridiculously long set up of the story in the first quarter, that could have been easily reduced and had a more quick, easily understood impact. As it was so drawn out, the focus to the story becomes hazed and the inevitable fight towards the end of the film is all you want to wait for.
The dialogue seems to have lost its witty edge as well. The parents (Kevin Dunn and Julie White) are there as if to keep the fans happy without a real influence on the story, which is a shame because they were always a highlight to the scenes in the previous two. Shia LaBeouf (Sam Witwicky) still plays the scaredy-cat hero, but because he's got a knowledge of what the robots are, there's less surprise and more of a "LET'S GO!" attitude.
There's no human character written into the story that really stands out in the film. Carly (Rosie Huntington-Whiteley) plays the new Megan Fox and does live up the the expectations, but doesn't have the bad girl image alongside it, so she falls under the damsel in distress category which leaves her passive to the story. If John Malkovich (Bruce Brazos) had more of a role in the film, I think he could have really lifted it, but he was a cameo for a fun few scenes.
What is the saving grace of this whole film is the amazingly edited special effects. Even from the first Transformers film, I have always been amazed at the quality of the visuals. So much of this film is in slow motion as well, so you can fully be in awe of the minute aspects the editing team have created - Such as the Transformers changing from car to robot, and the way they fight and break each other.
With this means the events are just so entertaining to sit and watch. So what if you've seen Bay destroy almost every landmark known to man! He'll always find some more and it will still be just good plain fun. And I think that's the whole point of these films - You're not there to be emotionally moved by the acting or the morals of the story, you're there to watch robots fight and things blow up. There's nothing wrong with that, and anyone who tells you otherwise, well, you can just class them uptight adults who want to neglect their inner immaturity rather than embrace it.
As for the 3D? Well, this is one of the exceptions. It's the little details that should be in 3D, not just guns pointing towards the audience, and that's exactly what happens in this - Even sun light reflections. This film makes the war among inanimate objects quite beautiful, actually.
Yes it's long, yes I was disappointed, but I still left the cinema thinking "Those fight scenes are bloody brilliant to watch."