Game still needs some optimization work I think. Seems to have a memory leak somewhere that shows up after several hours of playing, and I'm getting some herky-jerkiness despite blowing recommend specs for "High" out of the water. It probably has something to do with turning up MaxDeadBodies, but I dunno. Seems weird that I have hitching issue.
That aside, the beta has been a blast. Some people lament the loss of KF1's two-entry corridors, and camping in a line of guns for 7 to 8 waves. But as Medic, I'm really appreciating the chaos and bedlam the new game has brought to your typical camp & spank-fest. I spend as much time running through packs of spawned ZEDs to line up heals on my teammates as I do actual killing. While the game looks and feels like KF still, it's picked up a few additional tweaks, like sprinting, and melee bash to break yourself out of corners where you've been pinned by ZEDs, that the whole game feels like a step up in terms of fluidity and professional shine.
There are things here and there than KF1 vets might not like as much in the sequel: maybe you miss the sexual innuendo trader. Maybe you preferred the old "drunk guy at a pub" voice overs for characters. Maybe you thought the old Scrake was more threatening looking than this one. Generally though, I'd challenge any fan of KF1 to not enjoy this game. When you start playing beyond normal and the waves get longer, the enemies get tougher....it becomes a frantic fight for survival every wave, and I love it.