The built in WI-FI goes further towards the dream of a telescope tether carrying only DC-POWER through it, one less USB connection, which means less traffic on any remaining USB connection, and less chance of a USB cable imparting any noise into the camera.
How does Canon handle the WI-FI? Once you establish the WI-FI link between the 6D and the Canon software, does it appear equivalently as a USB connected camera from the point of view of software like Maxim, or BackYardEOS? Does anything support the 6D for shooting?
I haven't had it under the sky yet, but the attached picture of my bench was taken by a wimpy closet light at freakin' ISO 8000 !!!!