Interesting responses. I have the following:
1. DK2 - not a serious headset, obviously, but certainly my first toe dipped and where experienced ED initially, and then knew there was no turning back. I didn't play properly as the resolution was too low, but what an effect. I've kept this headset because... retro?
2. Rift - Wonderful, easy to use, solid as a rock and a great performer. I still have it plugged in because the ecosystem is just so well screwed together.
3. Vive - I have one, boxed, as I'm using the base stations for my Pimax (more on that). A good performer, but not great in Elite (maybe the lenses). I've not spent time in ED simply as the Rift did the job and did it well. Cheap 2nd hand now.
4. Lenovo WMR - too cheap not to try, and inside-out meant my laptop could stand in for the full Rift set up. Unfortunately I'd been spoilt with mechanical IPD adjustment I can only get a clear eye at a time (my IPD is very low; sub 60mm). I've lent this to a friend as I can juuuust about get a picture I can live with by swapping the foam, but it's not really worth the hassle. I may sell and replace by a 2nd-gen headset since they are all sounding very promising. The good; display, comfort, easy of use. The bad? IPD ruins it.. no audio.
5. Pimax 8k - FoV is life. Well, okay, it's like the DK2 of "the future". It's a pain to get right, but when you do, ohhhhh boy. ED is a git to get this right with; It has it's own Quality sliders, on top of Steam's, on top of ED's.. so get that within the sliders and you get a GOOD experience. My i7 is a 3xxx series and I have a 1080Ti and I've had a solid 80fps (with brainwarp, so 40fps) and it's really really nice. But, there's too much to set up, and when tracking does go, it likes to take it's time to come back. But, I don't play ED with anything else now, so it can be done!
The future has to be 140degree FoV; will the Index do that? I really hope so as I'd love to see a plug-n-play Steam headset (or Oculus if they'd stop chuffing about with the S nonsense and give us v2) that "just works". The Rift did; the Pimax does not. It's sooo close though.
I still see myself with multiple headsets (cave/living room/travel), and they all can fill different uses, but for ED it's Pimax, and room scale? Jury's out for me. I think we'll see it soon enough.