I caught this earlier today. It was interesting to go through a set of emotions as I watched:
"This is dumb" ... "Well, this actually isn't too bad if you just embrace its stupidity" ... "Ok, this is just stupid" ... "God, this feels long. Are we sure this is the same length as the first?" ... "Yeah, I'd be okay with this getting rebooted with a different director."
I think the main problem is the inconsistent tone. I've accepted - and have even grown to somewhat appreciate - some of the dumb aspects of his Transformers movies... the robots that act like poor ethnic stereotypes for unexplained reasons, the fact that there are baby dinosaur robots in this one, the characters that get introduced and then forgotten about, the unexplained continuity problems, the lack of logic in explaining why things are the way they are, its transparent attempt to create a "strong" female character by making her a professor. But what I can't abide by is just how long this film felt even despite its frenetic pacing.
It's like watching something that's surprisingly engaging when viewed in a very specific light, but then having its few good qualities ruined by the fact the film is never willing to fully commit to its stupidity and is always 45 minutes too long.
There's a solid version of this film that's 1 hours 40 minutes and either eschews its broad caricatures for solidly written humans or embraces these caricatures and doesn't try to include "heavy" moments from time to time (little orphan Annie girl, Optimus Prime monologue at the end, etc). The film is caked in bathos of the worst kind and I'm not even sure if it knows it - often shifting from dumb humor to SERIOUS MOMENTS with the flick of a switch.
But yeah - I agree with those who say this isn't the worst one. I'd put this ahead of the last one and TF2 for sure. But TF1 still remains the only truly enjoyable one IMO.