Well, storyline is good, but on easy and medium you can whip through it quickly. Online and Co-Op is th best.
Really going online against others is the best. It's fun, quick and easy. Autobots vs. Decepticons. You have 4 classes, scout, scientist (healer/sniper), leader and tank. Best part is you can customize your online characters color and chassis style. I do wish you had more options or could customize more.
For those that did pre-orders, you were treated to an extra skin. Shockwave (scientist/plane), Jazz (scout/car), or Demolishor (tank). Alas these are only for multiplayer.
All in all, this game is fun and has much replayablility with it's online modes, leveling up online characters and co-op options.