I'm on holiday in Vietnam with a 70D and 6D, and several lenses. 40 STM, 24-105L, 70-300L, 18-135 STM.
The 6D is "my" camera - and it delivers. I put some photos on my gallery to share. No post processing done. My wife claimed the 70D (that I bought for myself) recently and so I bought her the 18-135 STM to make it a useable camera (so I could keep the 24-105L on the 6D). She did a nice job on the pic of me with that lens, and to be honest the lens has not left the 70D body since we got to Vietnam.
There have been a lot of questions lately around the 40, the low light on the 6D, the sharpness of the 24-105, etc. Just take a look at what I've published for yourself. I was in an aquarium and an arcade with this 6D/40mm combo, and the camera performed superbly. At 25K iso. (I saw a lot of EOS rebel and Nikon users frustratingly looking at their cameras, honestly). I absolutely love the 6D/40mm combo - check out the sharpness of this photo- and the DOF between left and right eyes. That's not even wide open. So if you're on the fence on a 50 vs a 40, I'd offer that the 40 not only delivers, but it's a much more compact package that is ridiculously sharp. I'd gladly sell my 50 1.4 based on what I've seen thus far. This picture was on an amusement park ride (in Nha Trang). The camera+40mm is small enough to "act" like a POS. Rather than the full up 24-105L+6D as is my normal walk-around package.
The 70-300L is wonderful, but it's a big kit to lug around. It fits in my backpack though so I'm glad I brought it, even though it's the least used lens on my trip. I wish it weren't white; in shooting street scenes in crowded Vietnam cities I feel like it's got a big "look at me" sign on it.
The GPS and WiFi on the 6D are fantastic. The GPS is quick to acquire, and easy to toggle on and off. It allows me to log my location, which I can then stamp to other pics via Aperture, and the wifi allows quick posting to Facebook via my iPhone. Once you have the wifi setup on either body (a 3-5 minute job), the upload to the iPhone is really painless, and the settings are remembered.
Once I get home and can do some proper assessment, sorting, PP, I'll post some more pics to my gallery. But in the meantime I really wanted to share my thoughts on this incredible system.