It won't win any "Best Game" awards, but it nails the nostalgia factor and does multiplayer surprisingly well.
The story is not very immersive, but there are few gameplay rewards like some unlockable artwork. HOWEVER, the final boss fights are as epic as they come, and themselves alone are worth playing the short campaign for if you're a fan of the old-school IP. Online co-op is kind of a necessity due to the stupid AI allies, but the online co-op experience is fairly smooth overall.
There's a good amount of fanservice, and the G1-based characters were brought to life faithfully. It's a nice journey for a Transformers fan, with moderate replayability and online modes to keep you busy.