well if there are issues you can always get the dock which will allow you to correct it. So it isn't that big a deal. If you have the cash and need a lens of this FL go and get it!
I've read a little about the dock....what does this do exactly? Isn't MFA body specific? My understanding is that the dock was to allow for firmware updates and compatibility with canon bodies released in the future.
I was so pumped to check out this lens at the Sigma booth (w/their 5DII) at WPPI, but I don't know if it was the lighting (typical expo lighting) or not, but I couldn't get consistent AF with half my shots. Perhaps a bad copy, but being that it was the Sigma booth, I would've thought they'd check out everything before the show, especially knowing folks like me would be demoing their lens.
Contrast that to the Tamron booth where I tried their 24-70 VC, and it was dead on every time.
I've owned a few Tamron and Sigma lenses (Tamron 17-55 non-vc, and the vc version), and the sigma 50 1.4. Never had an issue with AF on the Tamrons (other than the non-vc version being crazy loud) and the optics were great. 50 1.4 was a miss for me though. Did not want to jump through hoops to get a good copy and ended up returning it 3 weeks in. Was hoping sigma got the AF figured out in the 35 1.4.
I'll probably give the sigma 35 1.4 a shot, but will return it outright if I have AF issues with my first copy.