So the players got to spend time during the two weeks chatting, arguing, trying to get each other into trouble with their boss (Gipontel), sharing food, deciding what to do with the prisoner, learning more about the prisoner, and other such things for about 7 pages worth of forum posting. This meant that during the sessions we had more free time for the actual event-based stuff while still allowing plenty of room for roleplay and character development.
It also gave me a chance to resolve a few waves of zombies and expend some of the huge amount of ammunition they had without wasting time rolling heaps and heaps of dice at the game table. In other words, it was certainly a worthwhile addition to the game. The only trouble was that one player really doesn't do forum play but he was content to have his character be quiet and sit in the corner and wasn't annoyed that he couldn't partake as he's a bit more of an Action Hero-style player (though he does love his character development, he prefers to do it live and in reaction to interesting things rather than sitting around a cold cave).
If you'd like to read prior articles on this campaign, you can find them here.