I migrated three years ago from Nikon SLRs (801, 601, F80, with their excellent Nikon lenses) to Leica (MP). The Summicron 1:2, 50mm is my best compagnon, but I also love the summicron 1:2, 35mm as well as the brand new Summarit 1:2.5, 75mm. All this costs, of course, and arm and a leg! but I think it is worthwhile. My pictures are sharper, because of the lenses (I don't think any other manufacturer can match them) but also because the Leica shutter is so quiet and steady - I can easily make a sharp shot at 1/8 where I had trouble holding my SLR Nikon steady for 1/60! Maybe equally important to me is the image quality in terms of contrast and brilliance - I've never been able to achieve the same thing with the old equipment. Yes, yes, I know, now I have to show you the proof with my pictures, and I'll come back to that soon.
good luck to you