I have this camera now for a few weeks. It does exact what I expected it to do and is very useful for the things I do. I do use the 6D for both, stills and video. Coming from a 7D it surprises me that it takes still photos in livemode with aspect ratio 16:9, the 7D made them at the 'photo-normal' 3:2. I can't fine any menu-setting to solve this. I spoke to a Canon promo employee last weekend and even he couldn't tell me why this is and it even surprised him. Hey expected it to be fixed with the first firmware update.

Do we all have 16:9 still pictures when taken in livemode? Or did somebody actualy solve it already?

On the 5DIII it works like this...
In video mode and you take a picture you'll se a 16:9 picture. But if you open the still in canons photo editing program (the one you got with the camera). If you then click on trimming tools you se the 16:9 crop at the 3:2 picture. You can now change the crop to what ever you like. You probably se the crop marks as soon as you open the editing program.
I don't know if it's the same on 6D but I'll be suprised if that came up with a new way.

Cheers

Edit:
On the 5DIII I'll think you can change that in the menu... Maybe the same on the 6D?