Rather than trying to explain everything via email, they invited us out to their offices in Bellevue, Washington. That alone speaks of a developer that really does care about its fanbase. So, after making arrangements and booking the time off of our jobs, we flew down for a day to take a quick tour and talk with the guys at Valve.
We got a chance to take a look at L4D2 (including the version that was shown at PAX) as well as ask questions to the L4D/L4D2 team.