I've used the 6D for studio shooting a few times now and it's light, simple to use, and I'm very happy with the quality. The 7D now feels like a tank. Up until yesterday I had the 6D connecting through the studio wifi router as an infrastructure connection. That meant no direct connection between it and the iPad I wanted to use to show the pictures. I found later that this added a delay between a quick unfocused version of the preview and a clear version to replace it. Sometimes up to 20 seconds. Not good. And, this doesn't allow for location viewing on the iPad since I'd be away from the router.
So, I changed to the peer-to-peer option that set up the 6D as an access point that the iPad could directly connect to. This eliminated any delay of the preview image. And, as we shot on location I could hand the iPad to the model to look them over to get an idea of how her posing was and what I was getting.
Other than forgetting the iPad on the ground and walking off leaving this bright pink (don't ask) fully loaded iPad in a busy park, we got some good use from this feature. Oh, and there are plenty of honest people around. I figure 100 people walked right past it and left it sitting right there. Good heart workout without having to run!
On the drive home the model went through the whole shoot and deleted some obviously bad shots. That also removes them from the card in the camera so be careful letting people use that feature. It can be turned off. She also stared the ones she liked and this is very handy since those stars are added to the meta data on the camera because when I imported those shots into Lightroom they had the stars set. I can see myself looking through shoots this way and trimming the fat before an import.
One thing to note is that I found it was easier to have the camera and iPad set to stay on all the time...or at least the camera since it's the access point. If the camera isn't on, the iPad or iPhone can't see the pictures. The battery in the 6D seems to handle that just fine. It last as long as my 5D or 7D, even with wifi turned on.
This wifi feature has turned out to be as useful as I'd hoped. It's certainly becoming a standard way of shooting for me already.