I think I have an explanation for why a number of users of the new Leica M, like Mark Dubovoy
and Tim Ashley
find its live view focusing inferior to using the traditional range-finder mechanism. In short, I suspect that this is because the most natural and convenient way to use live view on a rangefinder has the lens stopped down to the taking aperture: SLRs and the new compact system cameras instead normally hold the aperture wide-open during composition, only stopping down at the last moment during shutter release, and this intensifies out-of-focus effects, making manual focusing far easier.
I have a similar experience manual focusing with the small apertures of the Olympus 12-50/3.5-6.4, where I am often taking at close to maximum aperture; it is far easier to focus manually with the brighter, adaptor mounted, 12-60/2.8-4 or 50-200/2.8-3.5 lenses.