Music was just right for a zombie game. I thought it was neat that you had the graphic novel style opening; and then it was a little jarring that the graphics style of the game was so different. For a shooter, I think it really helpful to have a crosshair on screen to show where you are aiming. Mouse look camera control is probably also more common as it feels better.
I liked that the sniper rifle seemed like a one-shot-kill, however there wasn't a good chance to feel like a sniper. When I got the machine gun, that was pretty fun but ran out of ammo quickly (understandable).
The zombies really were relentless, it was full-time danger.