So I borrowed this off a mate.

It's passable. Linear third person shooter is about the most tired video game genre so that doesn't really help it. You run, you jump, left trigger for over the shoulder aim... there's nothing really new here. The battlegrounds aren't big enough geographically and conflicts aren't large scale enough for the transformation to be anything more meaningful than a gimmick.

The first level is fairly good but it's mostly downhill from there.

As an aside the new Optimus Prime design is hideous - it's far too bulky and it's not helped by the running animation, which when combined with the really boxy legs and torso looks really stupid.