A couple of people in this thread mentions Op/Tech straps, so out of curiosity I went looking and found their web site.
While browsing, I found this nifty looking little rig:
http://optechusa.com/product/detail/?PRODUCT_ID=4&PRODUCT_SUB_ID=&CATEGORY_ID=4
It's called the Bino/Cam Harness. It looks odd, but it also looks comfy, so I started playing around with some of my spare camera straps, and managed to create a fair aproximation of the Bino/Cam harness.
It really does seem to be comfy. It takes the weight of the camera very well, and puts it all on the shoulders instead of the neck. It's got enough play in it to let the camera hang on my stomach the way a regular neck strap would, with enough play to get the camera to my eye in either portrait or landscape orientation comfortably.
The next time I go anywhere where I'll have to carry my camera around for several hours, I'm going to try my home-made version of the Bino/Cam. I think it will be even better than my old camera strap.
ETA: And I just realized why this whole thing feels so familiar - Robert Shaw (Quint) wore something very, very similar in
Jaws, to hook onto his big fishing rod.