The M6 TTL x0.85 was my first film Leica, and forever will be my favorite. I love that the shutter speed dial turns in a correct way, and the LEDs in this M6 are my favorite way to interact with a built-in lens meter in any camera, because the lights on both sides communicate under/over exposure not just in a binary way by being on/off, but also via intensity.
The viewfinder flare is exaggerated online IMO. I learned about the existence problem by reading about it online, after almost a year of owning the camera. But once I could reliably reproduce it, of course it became the most pressing issue of my life and I had to send mine to DAG to upgrade the finder to the MP standard. Another improvement I recommend is masking out the framelines you don't use. In my case the camera only shows the 50mm and 35mm, another thing DAG did for me.
The battery lasts forever.
Basically, a perfect rangefinder!