Cant wait to see test images with it on the 5D, especially border crops, I never got the 50mm f/1.4 because I didnt like the optics, lets hope this is better.
The Canon 50mm is very decent. I had two copies and both good wide open and no CA issues. Focus is also nippy enough. I see some have issues though. The Sigma is gonna be interesting at the borders what with that huge 77mm element on the front and the feeling that the borders may be effectively cut off from the sensor. We'll see, but if that's the case then they should be good. I actually bought it from around your way Cornish ... Bristol Cameras. Trouble with those guys is whether they got the stock to back up the online shop