Massive difference for me, on the order of 50% more FPS in worst cases and doubling my frame rate in some of the GA planes.
I run the game at 3440x1440 on a 2080ti/8700k/32GB RAM with everything on Ultra, except for Terrain and Object level of detail which are both at 100. Normally I’d get around 30fps flying over LAX in the Cessna 152 with live weather, multiplayer, and live traffic turned on and my GPU utilization would be around 60%.
Now I’m getting 65-70fps in the same scenario with 100% GPU usage in both the cockpit and external views.
Same story with the Airliners, albeit slightly less of a performance gain. A320 at KDEN lined up on the runway would usually be around 23-30fps at best and maybe 45fps in the air, now I’m getting 40-45fps on the ground and actually hit 60fps briefly in cruise today.
Pretty incredible results on my system, and a few people are reporting similar gains on /r/flightsim. It seems like this might be taking advantage of GPU headroom that was not being utilized previously, but I have no idea why that would be since the patch notes in the hotfix are so insignificant and unrelated to MSFS2020.