I'm definitely not suggesting that sub-75(90 soon) hz/fps are ok for VR, but I'm also curious as to the drawbacks of Asynchronous Timewarp and why it is not essentially mandatory for every game.
Flyinside has 2 fps counters, one for FSX and one that is labeled Asynchronous Timewarp. I assume the FSX counter is showing the true framerate that FSX is running at and that the Timewarp counter is showing what the image being sent to the goggles is running at. FSX's framerate can fluctuate from 100+ down to 35ish depending on the density. As long as it stays above 55ish fps, the Asynchronous Timewarp fps meter stays locked at 75 and the image remains judder free. When fsx' framerate dips into the 40's then the Async fps meter goes down as well and Judder starts.
I guess I just don't understand the drawbacks of Asynchronous Timewarp. When I see the Flight sim X FPS meter showing 55 fps and I move my head rapidly left and right and it's just as smooth as a locked 75fps without timewarp, it makes me wonder why it's not being used in every game. I know it's cheating, but if your brain can't tell, does it really matter? Of course the best solution will always be to just never go below the target framerate, but timewarp sure seems to help massively in situations where you do and I don't really see what the negative tradeoff is.