If you buy this game, make sure you understand what it's all about.
It's not an action game (but it can be fast-paced at times). It's about
thinking and tactical planning.
Personally, I got tired of the single-player quite quickly, but playing
cooperatively with another person (and using voice over IP to communicate in
realtime) adds a whole new dimension to the game.
I'd just like to stress again – make sure you know what you're buying. Try
the demo if you're unsure.
Also, setting the game up to play through a firewall is insane – up to
10 ports may need to be opened on both peers (and it's not really documented
anywhere). I'll include those I needed to open:
UDP 6112 6500 27900 27901 29910 TCP
6667 28910 29900 29901 29920
I'm not sure all of those are necessary and I wasn't about to spend another
hour eliminating them individually. In the end, it only worked in one direction
anyway. Certainly not a firewall-friendly game.