I recommend this game if you are into shooting things!
There is a really good sense of progression in the game. It bounces between leveling you up and giving you new guns, so that you continually feel like you are becoming more awesome. The guns are varied and pretty insane at the higher levels, and it feels good to mow down 100s of enemies in that constant march forward.
The game is around 2 hours in length for the first campaign playthrough, which feels about right for the game. And you can always play the other modes or try to boost your score with an additional playthrough to get on the leaderboards if you want to spend more time with it.
Also the boss fights are pretty great, I like the fact that they don't turn the gameplay on it's head. They feel like they really belong in the game, while also adding a bit more of a challenge.
Would buy again.