I was in the development lab in Munich for one day but am not allowed to report my experiences or impressions here, except (maybe) posting a photo of the entry door.
I had the opportunity to test some of my apps on a real device. The time did not reach for testing everything that I wanted. A day was just much too short for doing anything in depth.
Another big problem was, that the Apple AppStore for the device is not available yet in Germany. So no TestFlight app could be downloaded. All my 40++ iOS apps could not be tested for compatibility on the visionOS this way.
It was not allowed to make screenshots or videos of my apps either, nor of me, wearing the device nor from the development lab itself.