I had such high hopes for this movie... Hailee Steinfeld is very appealing, but in some scenes, she didn't quite have enough emotion to really finish the moment. All in all, I give her a 'B-' for her efforts.
John Cena was misused in this film. Another actor could've been cast, and it wouldn't have made a difference.
With Bumblebee's mimicry skill, there could've been ample chances for humor and cultural awareness of the 80's... The radio 'language' was not used enough... the movie 'Breakfast Club' was referred to several times, but not in one way which might've been effective: Hailey's character could've started out darker (because of her father's death) and because of BB, she later could've blossomed like Ally Sheedy did, and not just superficially, but as a person because of the life/death reality that is surrounding BB - she learns that she is not alone in her sadness and becomes less selfish when she learns to care for BB and not just herself.
Also, when BB got his memory back, he could've become more masculine, but still remain gentle for Hailey. He was a soldier after all (as John Cena finally acknowledged).
Lastly, Hailey's little brother could've taught BB a karate move, which later would be of help to BB in a fight with one of the Decepticons. The Decepticons would not know martial arts of course, so a little robot like BB would be a formidable foe because of his new (a la Karate Kid?) moves.
Great attempt at the backstories, but so much more could've been added (and edited out). BTW, even though we can imagine what happened to the mean 'popular' kids, the audience still wants to see...