Follow up... I ran with my HANS device for the first time on Wednesday. I should also mention that I added 6-point harnesses, and fiberglass racing seats too.
Compared to just a harness, the HANS/harness set-up does feel like it rides "off" your shoulders. You can cinch it down just as tight, so you don't feel loose - more like someone has their hands on your shoulders tightly. The standard black vinyl padding is OK, but I found the vinyl edges sharp against my skin on my neck when I put it on/off. The stock pads are comfortable other than that (HANS sells upgraded pads).
While trying on the HANS outside the car, I was really worried about the restricted head movement. On the track, it never became an issue. The only time I was bothered by the restraint was while suiting up in the car (you can't look down at your own lap) and driving around the paddock (you cannot look over your shoulders for cross-traffic). On the track, I forgot about it.
After two or three sessions of putting the HANS on/off and strapping in, it became second nature. I didn't wish for the quick release straps at any point. I can get out of the car quickly with it on.
Overall, I am very happy with my HNS choice - now, I hope I never get to use it.
