I just got mine, and have had a quick 30 minute flight with it. The ability to look about is really handy, but I can say it’s not done my flying a lot of good. 
I think I may have to disable the eye tracking because it’s really distracting. Every little glance I make, say at instruments on final causes the view to change then as I glance back up it makes me make unnecessary corrections.
Zooming in to make changes to a GPS is especially tricky. Let’s say I move my head forward to set OBS. I look at the OBS button, then move my mouse to click it, I then look to the knob to the right, and move my mouse over that. I now glance up to look at the angle of the display to see what I am setting it to, and that movement causes the mouse to move off of the knob, stopping me from adjusting it. Any interaction that needed twiddling one thing, while looking at another was prone for this.
Probably switching to the other interaction mode would also work, but I never got on with that, and prefer Legacy.
Setup was extremely easy, much more than I thought it would be. I suspect as your frame rate drops the head tracking will become more jarring, though for my test flight I specifically choose somewhere out in the American countryside where there was no PG, and at a smaller airport to see what best case was like.
I didn’t get any eye strain, or headaches from the IR illuminators, something which I had read about. I wonder if that really stems from having to crank your head about while trying to keep your eyes on the screen. I can see that causing muscle fatigue.
Overall I’m really impressed. I’ve not used a tracker since TrackIR 4, so I’ll need to get used to it all over again.