It took some time to get used to it.. I just wondered if you have used it yourself. The reviews I read were generally good so I was a bit disappointed by my findings. Their 50mm got poor reviews.
It is too bad about the optics on that Schneider 28mm. It isn't awful, but it is not on par with the others like you mentioned, especially the Canons. The reason I say it is too bad is because it is a mechanical masterpiece. Well, I will pull back on that a little. There are some operating quirks to get used to, but the lens is purely mechanical, precisely geared, and a pleasure to operate once you are used to it.