Very fun. Highly recommended.
Since the release last week I've played through four times and I continue to enjoy. Most of the guns really satisfy and vary wide enough in style and function that each one feels unique. The way the zombies fall differant depending on how their killed and the shear volume of them toward the later stages was pretty impressive.
That said however the game is not without it's drawbacks. For one thing it's far too easy. As I said I've played through several times and the only time my barriers health dipped below 75% was when I decided to see how the shotgun and shotgun combination would work if it was employed throughout the final levels.
Also it would have been nice to have a few more levels. It really did feel a little short (but then again, if your major complaint about a game is that it made you want to play it more, I guess it really speaks to how much the game was enjoyed).
Great game and I look forward to whatever's next.
(sequal?)