It usually crashes on connecting for me.. I was able to get in twice, but the game always crashed before I could actually shoot someone. I guess there are timing issues you don't have when testing on a single computer or in LAN. When creating my own server, it looks pretty solid though. has some potential!

EDIT: I was able to play a few round with only me and painkiller playing. I guess the instability came from the higher number of players, maybe the BPS is too high for your server to handle. The native multiplayer tends to crash then.
The game itself is cool, with two players I couldn't see enough strategy yet, but I'm eager to see how the game evolves!