While I have never owned the 35mm Zeiss lenses, back when I worked at the camera store (4-years ago), we had several professionals who swore by them. I initially thought it was a bit of professional arrogance (e.g., "I don't use amateur lenses") until I saw several photos that one of the professionals had taken for a job, some taken by him with a Zeiss 35 f/2 and some by his wife (also a professional photographer) with a Nikon 35 f/1.4, both on separate Nikon D3's which were set up identically. Neither was shot wide-open (it was a large wedding).
The Zeiss colours were cleaner, more contrast, with less chromatic aberrations. This is in no way to say the Nikon lens was not excellent but once you saw the two together, the Zeiss was much better.
But! This is like drinking a 50-year old scotch and then having a 25-year old scotch - the 25-year old will be terrible. On the other hand, if you had a cheap blended malt beverage and switched to the 25-year old scotch, you would think it was wonderful. Putting the two pictures together, I could see the difference (two other employees in the store could not see the difference at all, neither could his wife who thought it was an expensive toy) but if you just stuck one picture in front of me today and asked which lens was used, I couldn't tell you; the difference could only be seen in direct comparisons.
If you never used one, you will never miss it; if you use one, expect that 90% of photographers (and 99% of non-photographers) will never be able to tell the difference. If, as an artist, you can see the difference and that difference is important in your art, then it would be worth it. As a B&W photographer, the increase in contrast would be nice (since the colour and CA does not affect my photos) but not for triple the price.