I can get either the Sigma or Canon 50mm 1.4 lens for the same price (around $449 CDN). At that the Sigma has the case and hood which are substantial cost (more than $100) for the Canon.
I see that both lenses have their issues (Sigma - possible misfocus, Canon - Fragile AF drive).
I know that a lot of users questioned whether the Sigma was worth the extra bucks but I don't have that problem here.
The other option is say scr#w it - buy the Canon 50mm F1.8 to learn about using primes and small DOF while waiting to buy the Canon 50mm F1.4 Mark II whenever it is released.
Thanks
Don
if you have a sigma service center near you have it calibrated as soon as you get it. wonderful lens. my fav so far 

