Here's how I think I fixed the issue on my rig (GTX 770 2gb, i5-4670k, 16gb, nothing overclocked, Windows 10 Pro, game on Crucial MX500 SSD):
I was having the same problem as the rest of you. Prior to the update, I could run everything maxed on ultra with only the occasional hiccup. After the update: FPS drop, stuttering, etc. to the point where it was unplayable no matter what graphics settings I chose. This was especially the case in career mode. I have not tested online because I'm still working on my skills. I tried Jason's recommendations, but they did not work, until...
I did a clean install of the game. I then applied Jason's recommended 3.001 settings with a few deviations. I put cloud detail on high and turned on HDR and SSAO because those settings are too pretty to pass up. Career mode ran smoothly (frontline activity on "scattered") even when several new planes entered the scene.
I will keep adjusting graphics and frontline settings today to see what, if anything, breaks it again. I do not own Kuban yet, so I will not be able to test that more graphically-demanding map.
Thanks to all here for pointing me in the right direction fixing my current favorite game and to the devs for such a massive update.