If you aren't a transformers fan, don't bother playing this game
Oddly enough, there are a couple of points in the game that are extremely difficult because of the way the game characterisations blend with the environment. Hence the difficulty ranges from extremely easy to extremely hard but overall, very easy.
I didn't like the way the game changed the story line a bit from the movie. E.g. Jazz isn't killed by Megatron as in the movie.
Each mission is very short and unlocking bonuses is very boring and repetitive. Seriously, wtf!? Overall the Bonuses were not even worth the effort except for the G1 skins.
There are some good points though:
1) The transformers themselves look very good and the transformations are great.
2) Voice acting by the few voices in the game are pretty good.
3) Background music is pretty good too, almost movie like.