Finally got a chance to play online with some other people. Seems pretty cool so far. I did run into an old Quake2 co-op problem that you should be able to fix in the game mod...

In ware2, in the room with the tank near the end: When players enter, the door shuts. If they die before pressing any buttons, then the map is sealed off and can't be finished!

Not sure, but there could be more of these situations in the game. :/

I'm sure there are plenty. The very next level has that spot where you step through a blue scanning area, which triggers an alarm, and turns on a bunch of lasers on the floor in front of you, as well as a wall of them behind you. You can block the wall for a little while with a nearby barrel, but it explodes eventually.

Well, that one isn't a game-stopper though. You can still go around the other way through the water pipes. (and it's actually easier to turn the lasers back off coming from that direction).

Hm.. I concede to your better recollection of the single player campaign. I forgot that those water pipes were the same level.