Initial impressions
Coming from the Vive the wider field of view and reduction in screen door effect were very noticeable. However, it felt like there was a smaller sweet spot where all the image was crisp. When I first put on the pimax 5k+ the distortion was prominent near the edges of the lenses (even on normal FOV), this has been reduced greatly by doubling the foam thickness. Getting the tilt of the goggles and the vertical position on my face right was challenging but the image is great when I manage it. I have a slightly smaller than average head, with fairly standard western features.
My hardware and performance
I'm running an RTX 2060 with a Ryzen 5 3600 and 32 GB RAM. I seem to be able to the games to run pretty solidly without any reprojected frames at normal FOV. The performance was much worse before I upgraded to this CPU.
Image quality and experience
In some games the wider FOV was really helpful, such as Xortex in The Lab. In others it was easy to forget that you could see more than with a Vive.
It's great not to have the god-rays that were present in the Vive, but I feel like there is some other kind of effect going making me aware of the lenses that I don't notice on the vive. Maybe a reflection of the light hitting around my eyes, I'm not sure.
Software
I had some issues getting going (using too new a version of Pitool) but it took me hours to get my Vive working properly so I don't judge Pimax to harshly for this. Some more explanation of the settings within Pitool would be useful.
Conclusion
The resolution and FOV of the 5k+ are definite upgrades on previous gen VR headsets, however the ergonomics out of the box were terrible for me. It took a fair bit of experimenting with extra foam padding and very careful positioning on my face for the image to look right. When moving around while playing games it often shifts to a position that causes what I think is chromatic aberration. If I can crack these positioning issues I think this will be a fantastic headset.