I dumped my 35L for the Sigma... Actually have owned the 35L two different times. The Sigma is a better lens in multiple ways.
Lack of bokeh CA
Contrast at f/1.4
The only thing the 35L is better at is color rendition. But I thought the 35L had the best color out of any L lens I have used. So nice... But I have not had much time with the Sigma outdoors yet to really compare.
But yeah, no regret dumping the L for the Sigma. It is a better lens for less money. No brainer.