Here's a really interesting forum post I found with samples from five different 35mm lenses including the 35L, the Sigma Art, the Samyang, the 35 IS and a Nikon one too.
It's in Vietnamese, trnaslated via Google, which makes it quite funny to read... but hey, the images are the important part! The Sigma really impresses me with its flare resistance, lack of purple fringing etc, as does the 35 IS - clearly both benefit from their modern design improvements.
http://translate.google.com/transla...s/showthread.php?t=189358&hl=en&langpair=auto
I'm also currently in the market for a 35mm lens to add to my wedding kit. I am hugely torn between the Sigma and the 35L, I've discounted the IS as I love shooting wide open... as I say, the Sigma undoubtedly benefits from modern design improvements over the 35L, but from shots I've seen the L has that 'je ne sais quoi' to its out of focus rendering.
My major worry, though, is all the horror stories about the Art's focus issues. So many people are reporting inconsistent results that are unfixable by focus adjustments
The dock is a great idea, but why did they bunch 3 of the 4 options right up near the MFD? This is an issue, especially as many of the problems people have are between 2m and infinity (i.e. if you adjust it to nail focus at 2M, it's off at infinity).
I have nothing against Sigma, I love taking my 50-500 out to photograph some wildlife at a hobbyist level, but I would hate to have any more inconsistent AF issues to deal with at weddings... I already have the 50L if I want to put a lens on that'll give me lots of beautiful but OOF images