Well, I played the first Beta and Dest fixed a lot of the technical issues (Ear-bleedingly loud sounds, various crashes, excessive motion blur, ect), but a ton of the gameplay issues were still alive and in full force, so everyone left.
Gotta make it so that it doesn't take multiple Assault Rifle clips or several Sniper Rifle headshots to take down Zeds in a high-player-count game. And also gotta make it so Zeds act more intelligently around defenses.
I think the big problem is how easy it is to mow down the zeds in long-range, wide-open areas (Everyone knows how easy it is in KF, with Mountainpass, so it's no surprise that it's easier with rocket launchers and gun turrets), but how ridiculously hard it is to take them down up close due to their massive HP, Damage, and movespeed.
Also, the Patriarch was ZERO fun to fight. A billion HP, so it didn't appear your guns were having any effect, coupled with the usual ridiculous damage he can throw out was a bad combo...