I understand Yeats point. But I think we may be reaching a point where all that is changing. Once all cameras have sensors that have 13 EV of dynaimc range and have relatively clean ISO6400, then digital bodies IQ differences will stop changing every 6 months or every year. We've been gaining a half stop or a stop every cycle and we are just about to the point where cameras are seeing in the dark and highly detailed stuff can be pulled out of pitch black areas.
So then it will be the user experience that will sell the camera. Assuming nothing else changes, this all works to Leica's advantage because they always lag a generation behind in the "tech" stuff. The optics never really change (except the computer modeling means the other lens makers have closed the gap!) but Leica bodies always have last years LCD screens and the sensors have always been a couple stops behind the current generation. They've gotten by on ergonomics, the rangefinder experience and their good name (and build quality). Eventually all camera will max out IQ....there is a limit, and then the user experience will trump all.
I think I'm yammering....must be time for bed.