It is quite remarkable how much noise the notification about the Leica M7 makes in the photographic world. The aperture priority exposure automation of the M7 was a first for the Leica M. Till 2002 everybody had to cope with the M6 method: balancing two LEDs by shifting manually aperture and/or shutter speed. In those days it was referred to as pure photography: learning the basics of exposure metering was a must for any novice in the craft. The method pioneered in the Leica M7 is still the exposure method of the M8 to M10. There is no other option if we accept that the lenses have to be handled manuaally and the camera has no electric or mechanical connection to inform the internal microprocessor of the selected aperture and adjust the shutter speed accordingly or the other wy around. What Leica accomplished was standard procedure for all Japanese manufacturers of that time. But Leica was limited in its options because of the manufacturing process and the choice of the mechanically governed horizontally running cloth focal plane shutter.
The fact that silver-halide afficionados within the Leica world select the MP and M-A as their primary tool speaks volumes for the trends: the film community wants a basic camera without any automation (one cannot seriously call the M6 metering system an advanced version of camera automation). The digital community (a much larger segment of the Leica camera buyers) wants as much automation as possible: even the M10 is not enough and there is a tendency for Leica CRF owners to buy a CL or SL to make life easier, but also adds to the weight and volume of the camera they have to handle.
Many comments claim that the instantaneous exposure mechamism of the M7 allows them to take pictures that are impossible to take when one has to measure the expusure with the M6 or even the clip-on exposure meter of the M3 to M4-P (excepting the M5 of course). This is nonsense because a scene illumination does not change that fast. You can take one incident light measurement and use this as a reference. The rest is simple guess work based on experience.
The functionality of the M7 is transferred to the functionality of the M10. With the exception of smooth changes of ISO settings, direct control of the picture on the back screen, selective spot metering and focus control on screen, the photographic experience is the same. What is embraced in the digital M cameras is rejected in the cartridge loading bodies.
There are discussions about the question how and why to buy a cartridge loading Leica camera. Mike Johnston on his blog remarks that the M7 is not a purist camera (evading the definiion of what 'purist' is) but that the M7 with the aperture priority AE enables the photographer (him) to take pictures (presumably in a successful way). Then he follows on his traditional mantra (and one joined by many Leica second hand sellers) that the best Leica film camera is the M4 (the one that should be the best mechanical Leica camera with the most elaborate manufacturing processes. (You can read in my new book that this is not the fact!). There are many hyperboles in his blog about the M7 and film Leicas and lenses (the reference to HCB and his Summicron lens is not supported by any factual research). The long list of comments shows an intense interest in the Leica things,but I have to say that not one comment breaks away from the standard and not very illuminating way of discussing the Leica, the rangefinder concept and the conventional film-digital diichotomy. I really miss Susan Sontag and her comments about photography. At least she elevated the discussion to a higher level.
It might be time to break out of the myth culture surrounding the Leica cameras and to discuss the virtues of the Leica CRF in a more sober way.
My view of the cartridge loading cameras: buy a new M-A (a good original M3 is difficult to find and the modern manufacturing processes, including material choices are now much improved). OR buy a second hand M4-P (the 75 mm frame is very useful) or any one the many M6 bodies on the market. If you are new to Leica and want to experience the digital path buy an M8.2. It hs its problems but coping with them is a very rewarding experience. It makes sense to limit yourself to ISO 640.