I think the J8M brings enough improvements over the J8 that with the right adapters I'd probably use it a lot more. It's very compact, the click stops are a welcome addition, and optically it's very good. Plus the fact it's Contax mount means, of course, that it's far more likely to work on a Leica without adjustment (assuming you have a good adapter, of course)!
<snip>
I think anyone who questions the performance of Soviet optics should really just grab a Contax and try out the various lenses on that platform instead - they are stunning. It's just a shame that a) the Leica mount ones aren't really for the Leica mount, and b) so many of the LTM ones have been butchered over the years.