I like it a lot. The game has Xbox plug-and-play, but it does it nicely, because it won't interfere with non-Xbox controllers.
It wasn't clear to me that R and Space were actually necessary, because reloading automatically happened, and upgrades seemed to happen just by choosing them, without pressing Space.
There were little touches that I liked, like the way that enemy pawns would bounce back after hitting them, and how the upgrade screen would give a 3-second delay, before closing.