Just bought some these, and tried them for first time today.
Although expensive, I guess you can argue the can also be used for other purposes, and they can't fall out of the sky and get damaged even if my Spark does.
I think they work as described. You get a nice viewing screen, but it does take a little getting used to. After two full
battery flights I felt pretty confident for basic operation.
Some caveats, which I may find adjustments for. Even though you're not closed up like with goggles, I didn't feel I could see what else was going on around me. I'd be a little concerned if I was in a sketchy area by myself, as I don't think it would be too hard for someone to sneak up on you and mug you or whatever. They are immersive. The clear lenses make the viewing screen hard to see I thought, even at golden hour, but I read that this may be adjustable with screen brightness. I thought they might be easier to see around, but maybe because i'm not using the nose piece. I will experiment more when I get a chance. The sun shades, (for me) are almost impossible to see through at golden hour. But they do make for a lovely viewing screen background. Maybe in really bright sun you can see through also.
One thing I noticed, is when I want to I can really focus in on something and concentrate on the gimbal movement, like if following something as I pass. I only used a wifi connection with the Spark. Did not have any connection or lag issues this time. But I stayed within an 800 foot radius. Didn't want to push it to far and have an emergency with an unfamiliar device.
When I was first setting it up, I had a heck of a time with the sensitivity -- as in way over sensitive it seemed.
I think I'm really going to like it, but I will come back if I note anything interesting or problematic about it to report.
I only have the Spark to use it with, so all is Spark related.
Edit: looking in the box, I just noticed there is an intermediate shade, so that's good. The one I should have used.