I couldn't agree more, in regards to the optical quality of the SL lenses vs M.
But referencing the new SL2, yesterday, I had the opportunity to play with a neighbors just arrived SL2. I had brought along my SL 24-90 Zoom and promptly snapped it into the camera's mount. Before I'd even powered up, something immediately struck me as odd; I, like many photographers, are accustomed to supporting heavy camera/lens combinations with my/our left hand beneath the lens. And when I did that I realized that I cannot effectively use the left sided, rear mounted buttons, and to do so I had to substitute my left hand with my right, an inefficient use of time and energy. While the left sided design might work well for the lighter APS-C Leica that can be managed in a one-handed fashion, no so with the SL2. Anyone else find this an issue?