Nachkebia, really? What especially did make you feel, the Summilux' ergonomics and build-quality would be inferior? I think, the Leica-lenses are built absolutely great and feel as nice as the Zeiss ones. So I really don't see much of a difference between the two. I especially adore the Zeiss Ikon system, 'cause Zeiss offers products that are equally built than Leica's and also are on par when it comes to optical performance, but for much less money. This is absolutely fantastic and I don't care at all, that the outstanding Zeiss products are partially built by Cosina (after plans of and under control of Zeiss), 'cause it matters what comes out at the end and this isn't inferior to Leica's products.
Just a bit of rave about my beloved Zeiss Ikon. 😉