My main use is iRacing.
I have just managed to get Motion Smoothing usable enough for testing in iRacing. On the Large FOV Motion Smoothing is unusable as it has the severe vibrating I described earlier. I discovered on Normal FOV motion smoothing is mostly usable so I maxed all the graphic settings on iRacing and turned Pitool up to 2 to force Motion Smoothing to lock my fps at 45.
It really looked glorious, I wish I could play like this all the time. My laps times were significantly slower. Motion Smoothing also made the image slightly blurry all the time and occasionally would start to vibrate a bit worse.
So for anything competitive like iRacing it is a useless feature. Perhaps if there is an occasion where performance does not matter and I just want my virtual world to look as pretty as possible I now know some settings that mostly work.
I’m looking forward to the day there is a Pitool without any issues where all the features just work.
Also in reply to some things you mentioned. With my PC it seems I can have much bigger frame dips than you mentioned and be surprisingly smooth. Keeping in mind I have a 5700XT and perhaps that is why our experience is different. As a general rule I can easily see the difference between 90hz and 120hz in other devices. I’m even often able to see the high frequency flicker of a fluro light when no one else I’m with can. On the PSVR going from 90 to 120 is sublime, going down to 60 is painful. I can’t recall if the Lenovo switches to 65hz or 60 hz but going from 90hz to that lower setting is also horrible. Unfortunately as I have a 5700XT my Pimax can currently only do 90hz. It reports as changing and when I switch to 120hz I’m force into a smaller FOV but I always have a 90fps frame cap in any mode and it doesn’t feel any different to 90hz. But unlike you I can drop to very low fps and barley notice a difference on the Pimax. I doubt I’d notice the fps dropping to 80 most of the time. Even at 65 it is surprisingly smooth most of the time. It is noticeable but useable and does not bother me on the Pimax even when it drops that low. I also ran a PB time at 60-65 fps.