For a few weeks the Canon 6D is with me, after I have read a lot about their image quality at high ISO speeds. For some time I wanted to "upgrade" to a full-size, after I first a Canon 40D (which was stolen from me), then had a 1100D and last a 50D. The move has paid off! With Adobe Lightroom (included here) and the settings for noise reduction can be up to ISO make 12800 readily Photos with very good quality in a hitherto unknown quality - better a few years ago than it is possible with APS-C cameras and ISO 1600 was. A dream come true, so to speak. Because I had to do it in the last few years with adverse lighting conditions. Now it is really fun to shoot atmospheric pictures in such extreme situations. About adapter to Altobjektive Leica, Olympus, Nikon, Pentax, Contax, Yashica and their foreign manufacturer can use (at Leica have to be careful with some lenses that the rear lens or a protective collar is not good cheer => against the mirror of 6D There are Internet sites that provide information, just search for it). For example with a used Olympus OM Zuiko 1.4 / 50mm or Leica Vario-Elmar 3.5 / 35-70mm can shoot fantastic good photos without disturbing Crop Fraktor if you want to enjoy with little budget full frame.
What I also like the 6D compactness and weight. Hardly bigger my old 40D. With the Canon EF 2.8 / 40mm, it forms a very compact unit.
I am very excited about this camera and can recommend them without restriction! Five star it has earned.