Link to MTF for sigma 30mm f/1.4 and Nikon 28 f/1.4 D

[Chad Gladstone]

If this is any indication then the sigma looks really good wide open even if there appears some substantial sharpness fall off at the edge of the frame. Contrast and bokeh also look promising - I can't wait to try it out.
http://www.sigma-photo.co.jp/lens/digital/mf30_14.htm

http://www.nikon-image.com/jpn/products/lens/af/singlefocal/wide/ai_af_28mmf14d.htm