Did you try the steam forum help section, deleting the config files?
My FPS tanked after the update, from 140+ to 100+ with huge stuttering, and deleting the config files put my FPS back up and made the game much smoother.
Not sure why along with the update the devs do not delete or update these files if they cause so much of an issue.
EDIT: I'm making a post about it because no one has been able to help me
I've been having the same issues. Game ran at 90-120fps prior to the update (which was still choppy and whatever because that's just what this game is) and now it's like 70-85fps (even though it doesn't actually hit that). It's horrifically stuttery to the point where it is unplayable. As well, it seems as though sensitivity is somewhat scaled with fps, so now turning (walking and moving the mouse like 90° or so to the side to shoot someone or simply navigate the map) doesn't even function half the time. I have no config files, everything as optimized as possible, and it was fine before the update.
Also it's weird that now fps drops about to 50fps when you look at the whole map. The game is unplayable for me at the current moment and it's sad because I want to try the new content out properly but this game won't even let me come back after some inactivity after getting burnt out. Thanks nwi xd
Remove all the contents of your app data folder found in...
You will need to re-configure video settings again. It will keep your bindings and mouse sens settings though.