I have both an M6 and an M2, with a Summicron 50 DR and Voigtlander Nokton 35/1.4, and a Jupiter 8 sonnar copy. I -love- using these cameras, for all sorts of work (the Summicron is amazing with TMX and FP4+ for clean, crisp, line-heavy compositional work, like busy urban street scapes. They won't do anything your other cameras can't, but they can definitely do certain things better than them.