I regularly get feedback on the Zeiss 21/2.8 Distagon (for Nikon or Canon) from readers that have obtained one. Invariably there is great appreciation for its fine qualities.
Laurence S shares his feeling about the 21/2.8 after returning from an African safari:
It's certainly my current favorite lens for the format... hands down my nicest shots from an aesthetic point of view were taken with the ZF.2 2.8/21, followed by the old Nikkor 55/3.5 Micro.
I’m not going to disagree— the 21/2.8 is a fabulous lens, as I discuss in my Guide to Zeiss ZF / ZE Lenses. Canon shooters especially should grab one and see what wide angle quality can be. Get one at B&H Photo for Nikon or for Canon.