Sounds like a great lens, and i think the Sigma 35mm is a great lens too. But an an aesthetic question here.
i never liked the 50mm format. Not on film (on my FM2) and not on my full frame Nikons (d700 &800). I have always preferred a 35mm as my "normal lens", or I like to go higher. Even on my 24-70 nikkor, i cannot think of the last time i ever shot using it at the 50mm mark.
Many moons ago, i used to run into a lot of people who felt the same way, back in the days of film. Have things changed that much? Bear in mind i am not questioning the quality of this lens, just the possible artistic demand for the 50mm size to begin with, regardless of who makes it or how much it costs.