What is it about the Zeiss 24mm that is so captivating?

I'm considering buying one of these lenses for my NEX-7 and have seen some nice photos made with it. And while most people here and on other forums seem to like it, I have read a few complaints, most of which I can deal with. But to the point, what is it about this lens that everyone loves so much? Is it a lens coating that makes colors "pop"? The sharpness? Is this a property I would definitely not see with a Sigma 30 or the forthcoming Sony 35? I know the Sigma is sharp, but is there something deficient in its color rendering?

I realize the focal length is also a factor; my main use would be street photography, as I travel frequently to Japan and Europe. I especially love Italy, which seems to be a rich tapestry of color everywhere you turn.

While I am not new to photography I am still somewhat new to the NEX system. So far I do not like the kit lens-the corners are too soft, and it's too slow. I like shooting in available light. Just trying to figure out if $1099 really is better than a $200 Sigma or especially the forthcoming $450 Sony 35 f/1.8 OSS.

Thanks for any help.