I have also a half years experience with Otus and I think it is premature to comment the Sigma lens qualties, all I think is that Otus is unsurpassed at F 1,4.
I must admit that, having looked at the available images I could find, including the http://lcap.tistory.com image examples, I believe the Sigma is a top notch lens. Sharpness, CA, distortion and bokeh looks very good. Color is still an open issue to me, since I do not know what kind of post processing they have been through, but it does not look bad.
Like you, I still doubt it will match the Otus, but it will have the advantage of AF. So I just made the decision and preordered the Sigma, but I will definitely keep my Otus.