I really love the core movement and shooting mechanics - it's some of the most fun I've had with just movement and gunplay in a shooter in a while. That being said, upgrades snowball to the point where whoever banks 4 kills in a single life first wins the game. It's fun with people on similar skill levels, but with random players it ends up being a little one-sided.
8.5/10, I'd make it so stats reset on a life but points don't (or maintain their penalty of -1) thereby making it less of a raw stats boost and more of a killstreak-style thing.