OK, as I actually have 2 identical machines except for the versions of piplay.
1# uses 1.1.92 - for comparison testing
2# uses what ever the latest piplay is.. As it's set to auto update when it finds a new one
I was a fan of 1.1.92 for a very long time as the fish eye and render quality of the newer piplay drivers just weren't doing it for me.
Some of my biggest bug bears were
Fish eye view
And the crappy Drifting
Difficult to make work when you want it to
Rubbish piplay software
Having to setup steamvr as well as games graphics settings
Having to run room setup EVERY time I want to use it
As 2.x piplay no longer uses steamvr's super sampling you can actually turn it right down the same with a lot of the graphics settings in game and just increase the render slider in the PiPlay app.. This helps with render quality and pretty much match 1.1.92 quality. my fps are usually about the same as 1.1.92 or only a few either side of it
The fish eye has virtually gone now. There is a very small amount if you really look for it but does not break immersion which for me is the ultimate goal.
The drifting has been fixed (one of my biggest hates of 1.1.92 along side ghosting)
Stability of 2.x is also much better, very rarely do I have to unplug /replug while tapping my head and rubbing my stomach just to get it working. Older versions of 2.x also had some issues of graphics clipping the edges of your game, this does not happen anymore. Admittedly I do use the PiPlay slider at the max setting of 3.0 but the 1080ti can handle it.
The only real downside I can see with the latest piplay version is the ghosting and @bacon has mentioned in these forums they are checking this out at the moment and comparing to 1.1.92 to see if they can get it as close to that version as physically possible.
Would I recommend it?
For me yes because the biggest improvement over everything was the drift fix! Completely changed my game.. So if you drift in 1.1.92 then most defiantly I would. If you don't and are still happy fiddling trying to get it to work each time you want to use it.. Then stay on the old version.
Just be aware that as pimax move forward they have already indicated that they are not working on any piplay version that is using steamvr compositor, but in the end it is your decision.