Well, we have visible progress this week. We distributed the beta succesfully, beat the stupid initial technical problems into submission - and got some scheduled games going! I didn't get a chance to jump in until Thursday, got a little time on the game with a fresh bunch of people, then jumped back in Friday afternoon/evening for a real, honest-to-god scheduled test session!
I wasn't counting, but I think we had over 50 people on, playing on Fallen Fighters and the map-currently-known-as "Apartments". I wasn't playing the whole time (some of us have to work too), but ran through some Countdown and Territory on Fallen Fighters, plus Firefight on Apartments.
We've actually been messing around with the dynamics of Countdown before the beta, adding in some extra touches, including a reinforcement wave mechanism for the attackers (as people got more experienced at CD, we'd been finding that defense outweighs attack too often - long story). It makes communication and timing important in CD, adds an extra dynamic, making for extra tension - and even more reason for the defenders to hang on, even when they are down to the last few men - can they force the attackers to use very limited reinforcements early in the round?
Anyway, I think the verdict on 50+ player Countdown was a resounding success. There'd been a nagging concern (in my mind at least) that it would turn into mass slaughter for the first 10 seconds, followed by a couple of mniutes of a few people creeping about. Might have happened the first couple of rounds, but I think I had underestimated the scale of our maps (and the skill of our level designers... [you owe me Krispy Kremes for that one, guys]). By the time I got to playing, the first 10-20 seconds largely involved 50 people vanishing into the terrain, followed by a couple of minutes of gripping combat. Every corner, hole, hiding spot, smoke grenade all house dangers that really matter. VOIP becomes very important, people supporting each other in small teams.