For that number of elements/groups and the expected increased weight from all that glass, this lens should be a serious improvement over the existing Canon and Sigma offerings and over the Zeiss Macro-Planar 50mm f/2.
I am looking forward to this lens and to the Canon replacement, because I am trying to assemble a primes kit and don't have a modern native 50-55mm lens yet. I am using ancient all-manual lenses I had already: Nikkor 50mm f/1.2 (amazing aberrations at f/1.2, can be put to use in a pictorial low-contrast effect, but usable as a regular lens from f/2.
, Mamiya-Sekor 55 mm f/1.4 and 60mm f/2.8 macro, with non-chipped adapters.
Sigma seems to be on a roll. I have contemplated getting a FF walkaround zoom as well, and the Sigma new 24-105mm f/4 behemoth has good reviews (not in local stores yet). I have the Sigma 35mm f/1.4, a very nice lens worth its price and bulk/weight.
Now back to my conditioning program, so I can carry that 35-40 pound photo plus camping pack come springtime.