I have a reply from Ed Trzoska - I'll have to save my pennies, but I could spend a lot more buying something newer, and given that he describes it as "one of the finest cameras ever made" he obviously likes them a lot!
He's right.
Just one little-appreciated point is that compared to Eg. their period competition from Leitz, the swinging wedge beam deflectors Zeiss used in the II/III must travel through a far greater arc than the prism Leitz used to deflect the patch of their rangefinders. According to Lipinski, this, alone, increases the precision of the Zeiss design by a four-fold factor over the screw Leica rangefinder, and that is before one even contemplates the gargantuan physical base length of the Contax. (But, EBL. Apparently that's the one and only thing that affects RF accuracy, according to some M6 owners.) 🙄