FSR has some serious artifacts in dark scenes when there's some light shining through - happens in some other parts of the campaign too (for example when the elevator lifts the plane up or in the first level before you start storming the subs).
However, it is truly a godsend in this game because I'm able to play multiplayer at stable 60fps at 4K with a gtx1660. And it looks way-way better than dropping resolution down to stay at 60fps at the same settings. Scenes like the one in the screenshot attached are very few and far between and the only multiplayer map where I found something similar and noticeable is Berlin in just a couple of spots. Makes me wish FSR was in every single game from now on, to be honest. For people with 4K screens and crappy videocards it works wonders - I never want to see 1440p (or even 70-75% render scale) on a 4K screen again, I'd rather encounter some occasional artifacts.