Linear gameplay and poor controls and camera angles ruin what could have been a half-decent game.
You will find yourself carrying out missions, sometimes as an autobot, and sometimes as a decepticon. The 'main' style of play is when you are in robot form, and you walk around with the nunchuk, use melee attacks on bad guys by swinging the remote, or shoot using the IR pointer. Shooting isn't always too effective though, and you'll find yourself in a true waggle-fest and your arm will get sore before long.
Your character has a health bar and energy bar. Energy is used for special moves, where you essentially transform and kill everyone around you. )This can be gimmicky, for example, Bumblebee transforms into his Camaro, does a couple of donuts, and that somehow kills everyone.) You can also use your energy to replenish your health if you're running low. Don't worry if you die though, you'll reappear maybe a screen back from where you were, and you have unlimited lives, so it really doesn't matter.
The decepticon missions seem to be more fun, where you are either driving, and can transform to a robot to fight, and transform back. Although the camera when you try to fight can be blocked completely by your character and you might have to transform a few times until you can see what you're doing. Even though this can be cool, you could just drive until the end and complete the mission. Another mission you are a fighter jet, where you can shoot missiles at enemies with the pointer. For some reason the gun on the jet can only shoot straight ahead, you can't change your angle to shoot toward a different direction which is annoying.
These control snags really hamper the game, and you will get tired of swinging your arms in most missions. The missions direct you where to go and you really have no freedom to explore. There are 'images' scattered around to collect, and there are some achievements which might drive you to keep playing.
Overall it's not a great game, I think there was potential, but too much waggle, too much linearity, and poor camera angles give the impression that the game was rushed, and resulted in a game not always enjoyable. I don't really recommend this game unless you are a true Transformers fan. There are much better game offerings out there for Wii than this.