I have the Sigma 50mm f1.4 EX DG HSM on a Canon 7D and love it. A little more expensive than the Canon f1.4 but it is built like a tank. Great balance on a 7D, fast and accurate focus for me. I would buy another one if anything happens to this one. I am still learning some of the vast capabilities of this lens but it just kills low light challenges. Also own a Canon 24-105 and 10-22. Just waiting for the new 24-70 (if it has IS I will purchase). Also rented the new (II) Canon 70-200 and it is on my wish list right behind the 24-70.
I should note that I never used the Canon f1.4, just went with the Sigma f1.4 based on reviews and I don't regret it for a second. It will be on my 7D throughout Christmas.