First up, get used to moving from a normal humanoid form of moving (i.e. walking, running, jumping) to transforming and driving or flying quickly because if you can't master this skill - you are doomed in the game. Not to worry though, the controls that will help you transform back and forth and move are a bit weird at first, but you will eventually get used to them. Once you do, the game play really gets easier, as you'll be able to move from one form to another so fluidly that you won't even remember when you couldn't do it. And, now, the game play will get really fun!
There are two different ways to play Transformers: Revenge of the Fallen, you can play in normal story mode, which loosely follows some areas of the movie, or you can play this one online against other gamers. In the story mode, you can play two different campaigns, Autobot and Decepticon, and both extremely loosely follow the movie so that you can follow a bit if you take the time to see the movie first. Since the graphics are so close to the computer animation in the movie, it's awesome to see them in action with you at the controls. Each mission is different, from the search and destroy to the races, and none really mirror the movie too closely, so it's no major problem with a different plot or differences in the game and the movie. One fun aspect to the game, each different mission that you'll undertake in Transformers: Revenge of the Fallen will take place in a wide open space, with tons of goodies to destroy for points, ammo, and much more. You'll find things like cars, light poles, tanker trucks, and even small buildings that are easily crushed and fun to smash.
From what I've heard so far, the missions do get a bit tedious after a while as they are basically the same as other games of this type. But, there are a ton of other challenges and unlockables that you can strive for to make the game more interesting and keep you occupied - some challenges even unlock some of the old school episodes of the original Transformers cartoon that I never missed as a kid.
During your game play, there are three main "forms" that you'll be able to switch into: vehicle, weapon, and robot. These are all basically self-explanatory, and each form will serve it's own purpose. You'll find out soon enough which forms you need to be in for different areas of the game and when switching back and forth can help or hurt you. I will tell you that the vehicle mode that I tried out was hard to master. It took me a bit to be able to switch over and smoothly move around as a vehicle, but the robot and weapon forms are awesome. Once you can master the different forms, you'll be able to transform into them quickly and kick butt with some sweet moves. If you get bored with the existing game play, you can unlock special modes like invincibility and super low gravity.