I have a 6D, and I'm very pleased with the AF system. I use the center point AF anyway, since at wide open, I need to make sure I nail the focus point.
As a back up wedding photographer, you really want to make sure that you are focusing on the Bride's eyes. No amount of fancy AF system can dictate that for you. You have to do it yourself. With the center point AF, focus is instant fast. I just focus, recompose, and shoot. Simple as pie .
The 6d certainly does look appealing. Potentially what I'll do is buy that kit B&H is currently selling and simply sell the printer and lens for a net of ~$800, giving me a $1200 6d.
+1 No brainer.