You don't need to shoot a single image ever to have a very in depth knowledge of how the technology actually works. Personally, with regards a technical question relating to Canon gear, I would go with the word of the real Chuck over Jay Paredes.
chuck westfall will also tell you the 6D has a great autofocus system.
It depends on use case. If you're not shooting action, the 6D does have great autofocus, it's quite accurate, and works in extremely low light. If you are shooting sports though, you wouldn't call it great. I'd take slightly less accurate AF for speed every time for sports.
I would say though, for me, I'll use IS all the time, unless I'm on a tripod. I rarely shoot at 1/1000s as I'm usually more concerned about deep DOF.
That said, I'm shooting animals on Tuesday, I'll have to test my AF speed with the 70-200 f/2.8 II and the 70-300L with IS on and IS off, to see if it's a notable difference.