Just so folks know. This is the 35mm f/1.5 not the 50mm f/1.5. The 35mm 1.5 lens is not a sonnar design, although I'm not sure just what design it may be. I've always termed the Canon 50/1.4 as the "Japanese Summilux" and I can say from experience that it is at least comparable to the summilux of its time. The Canon 50/1.5 is certainly a sonnar, and I can say from experience that its just as nice as the Zeiss of its time. I like it more than my J-3 mostly because of the handling and not necessarily the optical performance. But, the lens offered here is neither of those.
The 35/1.5 is rumored to be a nice lens, but not a super strong performer when opened up. I don't see the 35/1.5 up for sale too often, so someone must like them. The Canon 35/2 is a sought-after lens, and I can say it is nice -- Great contrast for its age and sharp even at f/2. If the 35/1.5 performs similarly, all the better because you have the option of more speed (although a tad soft) and then great performance stopped down.
BTW, this one sure looks nice.