Really good!
As I write this, I'm about to enter night 22 with 6 clips of flamethrower and 20 clips of shotgun for backup...
The start wasn't very promising (dude, I've got this brick...) but once I got my hands on the handgun the game got much better. I died quickly though, and on my current 2nd playthrough I opted for saving up for rifle ammo (a worthy choice, because of it's value for money). And now, I'm blasting them like there's no tomorrow... they're coming 5 at a time.
Awesome.