I'd agree with most of the posters here that if you enjoyed the first one, you'll probably enjoy this one too, particularly since it's longer and features more of the TF characters than they did in the first movie, especially the Decepticons. The entire (surviving) cast is in this movie as well as few new ones, which is always good for any sequel (if you liked the first one of course). I have mixed feelings about the live-action TF movies in general as I am more "wedded" to the G1 characterizations and storyline that I grew up with and consider the original (animated) TF movie (1986) one of my absolute favorite movies. It's hard not to be happy, however, that, in a stroke of genius IMHO, Bay was able to get Peter Cullen to voice Optimus Prime in the live-action movies as well.
