I've heard nothing but great things about this lens and have considered ditching my 14L II for it. I think the Rokinon is just as good in pretty much every aspect aside from distortion. Pretty amazing that they can pump out such quality products for reasonable prices.
Except, of course, for the weird and difficult to correct distortion But I agree, it's fantastic they can deliver such great performance at such a price.
Now, the things we're lacking, is amazing build quality, and....I guess that's about it aside from the crazy distortion.