As a fan of Transformers since watching the cartoon in my childhood years, I was very pleased by Revenge of the Fallen. It had more elements which connected it to the old cartoon, including the search for energon, the Autobot Matrix, and Starscream's rivalry with Megatron.
The only complaint I have for this movie is the same complaint I had for the first one: too much time is given to the human characters' quips and gags which have absolutely nothing to do with the storyline. It wasn't nearly as bad in RotF as it was for the first movie, but come on, we want more robots!
If you love Transformers, action movies, or outstanding CGI, SEE THIS MOVIE!