"The entire viewing experience is likely to be dim and squinty, compared to your M camera."
Squinty maybe, but dim? Just have the thing cleaned - mine (both RF and VF) are as bright as any camera I have looked through, including a new M7.
You know what's squinty? Trying to focus precisely with a .72 rangefinder. LTM Leica rangefinders are magnified 1.5x - or TWICE the size. They got this right the first time (well, III and after). And you can focus the RF! What will they think of next?! Whatever time you saved with the combined RF/VF evaporates trying to focus a fast 50mm on a pupil behind an eyeglass. Don't get me started on the .58 finder ....
Yes, the built-in 50mm finder is squinty (but it is not dim). Get a SBOOI for your 50mm and you get a magnificent 1:1 view - even with most glasses. Open both eyes for BINOCULAR vision, what will they think of next?
These experiences are based on being a presbyopic glasses wearer - 20/20 youngsters will have a different experience...
Not saying the M cameras are inferior. But they are a compromise in the name of convenience and maybe, under optimal circumstances, some small advantage in speed of operation.
(I should probably put on some flame retardant clothing after that - but I stand by my comments.)