Is it worth it? I find it interesting that Zeiss made it and kudo's to them for that. I dont think there is a whole lot of difference between a Nikkor 50f1.4, a Contax 50f1.5 and the new Zeiss, at least not in black/white. If you want the sharpest possible lens, the SC Nokton 50f1.5 probably takes the prize and if you want to have a "retro" look, either one of the older ones will give you that, albeit with more flare than the Zeiss C-Sonnar.
ANY new lens is interesting as glass technology is advancing and modern coatings will change the characteristics of an older formula in modern guise.
With the C Sonnar in SC mount it is abit of a mote point as far too many of these lenses will languish in boxes with collectors, rather than being used. With a production of 300 units - it will become a bit of a scarce commodity, which is too bad.