IThe best I've ever seen was a Steinberger L2 with the original "boomerang" pivot plate, hung perfectly. It's eventual failure as a commercial instrument had nothing to do with the ergonomics, and everything to do with the whims of intrument fashion.
I'd beg to differ on that one. The *only* reason that I got rid of the L2 was that I couldn't get used to it ergonomically, no matter how hard I tried. No, it did not suffer from neck dive, but that's hardly the only aspect to be considered when it comes to ergonomics IMO.
My $0.02 only...