I received my Pimax 4k a few days ago. I was looking for a 4k screen for my preferred program, Prepar3d. The issue in Prepar3d is that the other VR systems just don't quite have the resolution to display readable gauges. I was looking at the Sony Xperia phones, first the older one the z5 premium, which is affordable, but that was a no go because USB isn't going to be able to carry 4k signal. And the new xz premium is too expensive, even though it has USB-C, which theoretically can connect to DisplayPort. I decided to go with the Pimax because it is all ready to go. Then I was pleased to read here that it has a slightly newer version of the Sony z5 premium screen. So it's a win.
I am very pleased with the Pimax. It has a decent build quality. For an electronic product it has a higher than average quality. It's light and very comfortable. I am an audiophile, so I can vouch for the build, but the speakers are only a little above average. They work nicely and fit great with the comfort of the headset. If I could change them out I would, but I'm much pickier than average for sound.
Plug it in. Download the software and install. It works. And very well. While you don't get oculus/vive framerates ... you don't need them.
I was gonna finish this... but I got distracted. It's now been a month, and I'm still happy with them, even with the lens issue, which I'll eventually fix somehow. Great purchase. And with NOLO VR being 360 usable now, when it gets here and they finally get there with the software I will be smuggly satisfied I beat the heck out of Oculus and Vive for visual quality and price.