I've played KF for like 2 hours today. I've gone on the Demolitions perk from 2.6 million to 3.1 million. Then I exit the game after we all died, and when I tried to launch KF again, Steam got stuck on "preparing to launch Killing Floor...", so I exit Steam but now it was stuck on "syncing steam cloud", so I forced exit. Then I launched Steam and KF again, and the progress was gone. This happened 4 times today, without the game ever saving the perk progress. I lost interest in this game until this is fixed, and I certainly won't buy any more Tripwire **** from now on - the Mac version is just full of launching and crashing and perk-saving bugs that it's simply not worth bothering with.