I installed Steam VR beta tonight and have been fiddling around for about an hour.
I booted up project cars to try, I always use the same settings to test changes. I was gutted, it was awful
I had a look in the Steam settings panel and I had both Allow asynchronous reprojection and Allow interleaved reprojection. I turned off Allow interleaved reprojection and it was instantly much much better. I tried Allow interleaved projection on its own and it was awful again.
With just Asynchronous reprojection it was noticeably smoother than before using Steam beta and allowed me to up a few settings. I was running minimal settings with a SS of 1.1 before and the reprojection was almost constantly noticeable. I am now running a few medium settings and its nice and smooth.
I also tried MSI Electric City demo which I find useful for a VR benchmark and previously I could only run on quality setting of 3 and 4 with no noticeable reprojection, I can now run on setting 2 and even setting 1 with only a very slight judder / slow down in a couple of parts but none of the blurriness I used to get.
Very pleased so far, it feels like I've upgraded my GPU
On the downside I would imagine if you were running a system that performs very well and able to run a decent SS setting then you may find some of the games that do not allow in game SS will be a step backwards as I don't think you can SS after the update? I was able to run The Blu and Job Sim at 1.3 - 1.4 SS whereas after the update I'm locked to the standard setting with no in-game adjustment. This update benefits lower spec VR setups at the moment.