Well, I bought this lens from Adorama for $374 which is why I am giving this lens a great review. The focus was OK on my XT but better on my 30D. It had front focusing issues right out of the box so I had to send it back for recalibration. Thats was expected because all four of my Sigma lenses that I have owned all had focusing issues so I was not surprised. No big deal. Anyways, it came back superb of course. It is sharp wide open, even at 1.4! The contrast isn't there wide open of course but hey, you can shoot in the dark with this thing! Colors are nothing short of spectacular! One thing I should mention is that the left side of the lens is not as sharp as the center or right at 1.4, but that's pixel peeping at 200%. It is not noticeable beyond 2.8 and you would never tell on a print. I shot a birthday party entirely at 1.4 and f2 iso 800 with my 30D under fluorescent lights. I barely had to do any post processing, even the whitebalance was right on.
I personally find that I enjoy using this lens much more on my 30D or 40D because the focusing is faster and there are more focusing points to choose from which in turn makes the lens a more accurate when focusing especially at 1.4 or 2 because of the shallow depth of field. I am not going to compare this to L glass because for $374 what more can you want? (Although it is sharper than my 24-105 but thats a zoom) If you buy this lens, be prepared to send it in to recalibrate the focusing. Send it to Sigma New York, the will have it back in less than 2 weeks and you will probably never look back after that. For the price, you simply cannot get a better deal.