You can divide the six character slots however you want, but one each is of course ideal and it's really cool how the player that makes contact gets to handle the dialogue while the others watch. Combat is great when you can keep the pausing to a minimum. Loading and saving is a lot slower in multiplayer.
I have played this before, as have ksevcov, but infernovia is new. We've taken a few baby steps, but it'd be a shame to play this with anything less than a full party of six players. I don't think having played it before matters, but if it does maybe we can get more than one party going — so basically I want to play this too badly to politely opt out, lol.
I'm assuming ksevcov and infernovia are both in, and we can dive into stuff like difficulty setting, characters and party composition once we've got a full party. There's also Icewind Dale II and the Baldur's Gate games, but at any rate we'll be starting with Left 4 Dead this weekend so this'll come later.
We got the multiplayer working by using GameRanger: http://www.gameranger.com