Well, it looks like people were interested in trying the game without any communication whatsoever, as two separate GAF groups started up pretty quickly.
The results? With my group, mixed. As the Survivors, it was frustrating having to guard the slowest player on the team. This could happen with communication, but at least yelling at him would relieve some stress. Infected, I thought, fared a little bit better.
In the end, one team pretty much dominated the other. This is probably due to familiarity with the game, as most of the winning team showed they'd learned a lot of good strategies (e.g. not waiting forever in the saferoom, keeping a brisk pace, and good clustering; as well as some more map-specific strategies.)
My conclusion: if you're good, you'll be good without communication. However, having the mics, and using the text chat, does make things funner.
How'd the other group go? And, if you played in either, what did you think?