The pros: Gritty atmosphere, solid engine, runs under Linux (wine) with no problems
The cons: Very hard - I had to use health and armor cheats from time to time, music gets a bit monotonous.
My verdict: If you're a fan of the classic FPS genre, you'll probably enjoy this game. At $5 it's a steal.
I'd love to see GOG bulk up on it's FPS selection... there should be a ton of Quake 2 Quake 3 based shooters out there ready to scoop up.