I just like to say, that also I won't be buying this game, because it lacks the online co-op game mode. I saw this game being reviewed in TV and was almost sure that I'll buy it. Then I heard that the co-op mode, which was shown at TV, was only possible in one computer with additional gamepads. At first I could not believe it. I thought that these "poor guy" co-op mods were things in the past.
I think that this will be a very bad mistake when thinking the sales. You should of just delayed the release and coded that damned online co-op mode. It isn't so hard to do, just a matter of time to do it. You guys had made the game long enough allready, couple months more would not made any difference. Think Max Payne. They also coded the game like forever, but when it came out, it was rock solid and there wasn't anything missing with the lame excuse "we had no time to do it". And it sold well.
Just my 2 cents.. or actually, you aren't getting a dime from me, sorry.

My money goes to Serious sam II, which is also released at the same time and has a REAL co-op mode.