Save games and associated unlocked content from Shift didn't work as expected.

With the Native install, I was unable to contact the Shift servers, which meant no multiplayer capabilities. Using the Proton Experimental layer, the game boots and I can join multiplayer just fine, however there was significant network issues, with guns shooting as soon as the mouse was clicked, but bullets not appearing and flying to the target for another half second. There were a handful of other network related problems too, with juddering and problems jumping.

See the network issues above/below.