Decent, with noticable problems.
The graphics themselves, the music, and the general atmosphere are excellent. The details like buildings getting damaged are a wonderful touch. The controls are simple and effective. The dialogue is funny and doesn't sound noticeably amateur
Unfortunately, this is marred by a confusing upgrade screen (that among other things had me accidentally leaving the game every time I wanted to exit it), action too fast and frantic to keep up with, and skewed difficulty. For instance, there's no real strategy to react to anything other than to attack repeatedly... which won't save you if you're mobbed by mutants.