It's a shame when so many people that admittedly never have used the 35L is recommending 3rd party alternatives. I've myself never used the Sigma, but the 35L is a top notch lens. Not cheap, but it has a proven performance and quality record over 14 years which the Sigma doesn't.
also get the sigma 35mm f1.4 its half the price of the 35mm L and its better too
Ignoring the body-choice stuff (I love my 7d, and have been quite happy with the IQ:$$ ratio, but I'm also usually in pretty good light), I would get behind this recommendation of the sigma 35 over the 35L. Sharper, great colors, reviews all say the AF is as good as the 35L (never used the canon, so can't comment personally), etc etc.
Never said it wasn't- the point is that sigma has caught up, and the Σ35 is now every bit a top notch lens, for $900 new...
I'm glad that Sigma has been able to supass a lens that was designed 15 years ago. It will put some (if not much) price pressure on Canon's 35L replacement, and that is a good thing. I also think that the 24-70 II will be the prime competitor to the 35L II. According to TDP, the 24-70 II at 35mm is better than the Sigma 35 at f/2.8, and I would expect primes to beat zooms when compared within the same generation.
It also remains to be seen how well Sigma can adapt when/if Canon decides to change how it does AF in future bodies. Some people have been caught with lenses that will no longer work with newer cameras. Is that risk worth the 28% cost difference (in the US)? That's up to the individual users. If I already didn't have the 35L, then I would definitely consider the Sigma. Given that I already have the 35L, the slightly better IQ of the Sigma does not compel me to switch (and incur the transaction costs). It will be interesting to see how Canon responds to Sigma's new offering because I can imagine that Sigma is taking a big bite out of the 35L's sales.