Well… just tested 11.50 b1, and since I only use default scenery - didn't test ASXP yet - it works just fine with a gain of 30% ( more in some scenarios involving the usually heavy rendering of clouds ).
This is more than OK for me - I only use XP11 for PSX, so I always disable all joystick axis, buttons, as well as most of the keyboard shortcuts that can interfere with my PSX setup, and save the configuration :-)
So far I am enjoying the additional smoothness, although I am aware my GPU is not optimized for Vulkan - GTX 960 4 GB - and my CPU is that old i5 2500, and my RAM 16 GB DDR3 from pre-history :-). Just imagine if you're on an modern AMD GPU …
Very satisfied so far with 11.50, even if still in beta...