I don't mean to hop aboard the bumping bandwagon here, but I don't see KF ever being F2P, and it never should be.
I have been running KF servers since the start under multiple clans, and I have literally seen it all.
Rebooting the player base will KILL this game. All of the hassle is GONE, and I'd like it to stay that way. No one worries about having friendlyfire servers and those specific teamkilling group players joining and shooting up the entire server as level 6 medics, they still exist but they are RARE. No one worries about low level perk players using the wrong guns anymore, there aren't that many low level players left that do not know how to use perks correctly. There aren't even any medic farmers left.. I can't tell you how many players connect and see our ads go by and ask "what is medic farming?" (in ff, intentionally shooting your teammates and healing them. in regular mp, let a clot attack a teammate as you constantly heal them).
It is so good not having to ban players for breaking rules.. and we value that a lot just as we always have in our clan. We never tolerated it on our friendlyfire servers when they were up, but while we are strict on our rules now, no one even attempts to break them.
Even if it is a full squad of level 6 players on doom2 hard - we all still enjoy Killing Floor under vanilla rankings. It's just like someone having CS:S as their natural gaming territory. It feels good to be able to play a game you enjoy in the utmost of peace.