Inversion is a passable Gears clone with some nice ideas. The anti-gravity mechanic at the heart of the gunplay is a nifty idea, but it's also completely undermined by the game never really using it's USP to the fullest advantage. Instead, here we have a mediocre shooter with a forgettable plot, limp setpieces, and little by way of imagination besides enemies appearing on walls and ceilings.
If you're really, really bored this summer, and you've somehow played all of the really awesome games that have come out this year so far, then this is a good deal at face value (be quick, though, it runs out in eight hours), and we're honour bound to tell you about it.
But I wouldn't call it a good game.