The two things that the 6D is lacking that I think are important to a amateur/prosumer photographer are a second memory card slot and a pop-up flash. I just purchased a Nikon D600 for my father, rather than the 6D, because the D600 had the second memory card slot and a pop-up flash.
I could care less about WiFi and GPS....and video for that matter! I think Canon should have designed this camera geared toward purely still photography, and left out the video, which would have kept down the retail price and Canon might have been able to price it around $1,500. The Nikon D700 doesn't have video, and look at how many still love that camera!
I am fascinated as to why people feel a second card slot is worth a dime, I have had one for years and rarely use it, even then it is only for an Eye-Fi, something I could easily live without. Why do people value a second card slot so highly?
for example:
dual slots can be used as a raid setup so writing the same to both cards , that way you don't have to pull all your hair out of your head when a card goes corrupt 
or shoot jpg on one and raw on the other so on events you can ofload the jpg's quickly and keep the raws as backup
I disagree regarding card slots. Dual cards I'd say is more of a 'pro' feature. The average user is the type that will shoot in jpeg only, and consider 100 shots a huge amount, filling up a 16 gig card may take weeks. Also, the importance of files --- pro's need that redundancy, the casual user does not (yes they do want it, but no, it is not a NEED.). Now the pop-up flash I can see being useful and wanted for the casual user. that's my overall problem with the 6d --- it's kind of pro, but really not, and kind of casual, but really not.
I went on a fishing trip with my grandpa a few years ago and I took several hundred photos with my Nikon D700...the memory card I used was a Sandisk Extreme 8GB. I still don't know what happened, but when I went to download the photos, the memory card somehow got corrupt and all the photos were lost.
My Grandpa died last year, and I sure wish I had the photos from that fishing trip....if the Nikon D700 had a 2nd memory card slot, I would have those photos!
Now, do you get the picture of why I think a 2nd memory card slot is so important....you can't replace the moment of when a photo is taken! This has nothing to do with 'Pro' vs. amateur features!
I still disagree. It's still an issue of needs vs wants. I'm not trying to say that saving special moments isn't important, but - there is a clear difference between you hanging with you grandpa (and please do realize I'm not minimizing how important that is to you), as opposed to hiring a a photographer to come shoot you and your grandpa. The hired photog NEEDs the backup, because that is his/her job. You WANT the image.
If the want is that important then you make the financial sacrifice and buy something with 2 slots (i see by your sig you have a mk3, which means you have 2 slots). If you want that then you buy something with it. I'm more or less arguing the premise that dual card slots is a casual consumer NEED, and will sway buyers. I don't think that will - when it comes to the 6d what will make the difference is what the images from that camera look like - and whether or not your invested in a 'system' or not. That's why I feel like the 6d's flaw is it's not pro enough to be pro, but, it's not amateur enough to be amateur...
All that said, lets see this thing in the wild. I am on the fence between a 6d and a second mk3. For weddings I want both my bodies to be on a similar level in IQ. I liket he idea of a smaller second body because of the weight - i have no issue with a heavy camera - but, at the end of the night, i could see it being very nice to roll with a 6d + 16-35mm lens, that is if the images from it will look similar to the mk3....