The interesting point to muse about is the fact that the APS-C sensor size can challenge the 135-sized sensor in many situations as far as image quality is concerned, the only advantage of the larger-sized sensor is the ability to use all lenses without a crop-factor.
I'm glad Mr. Puts, a well respected Leica commentator, singled out this observation as paramount in his conclusion (i.e. APS-C is up to the task and likely to surpass Leica's aging sensor soon enough) although personally I look at the crop-factor and its impact on lens focal length choice as a two way street. The 1.5x factor certainly aids APS-C ILC camera users in fitting out their kit for lens perspectives in the slightly wide / wide-normal, and short telephoto/portrait and is a real boon for longer telephoto perspectives.
Given all the legacy lenses out there (that haven't been sent to the dump out there) enthusiasts have a lot of low cost good quality manual focus lens selection which I certainly appreciate even if Leica might not. I can hardly wait for my NEX-7 to ship and make suddenly useful all my 35mm manual focus lenses once more.