I say go for the 6D.
I had my mind made up I was upgrading from 40D to the 7D until I started reading about its sharpness (look at some sample pics). Apparently it has an aggressive filter of sorts that decreases its sharpness. Many many happy 7D owners have told me that you just increase sharpness in post. Now I know sharpness isn't everything, but if I'm upgrading cameras I want improved IQ. I don't want to have to do more in post.
Unfortunately the 7D didn't seeme like it would upgrade the IQ enough for me to justify the price. It seemed like it was just more of a feature set upgrade, which I didn't really care about.
Thus the 6D. It is the perfect upgrade for someone like me (and u?). I don't care about any fancy articulating screens (not on7D), super duper fps rates, and customizable AF systems. Sure those things sound nice. And sure I wish the 6D had a better AF system, but the one it has is sufficient and familiar to both you and I. It also boasts a pretty decent center point.
I have read all kinds of reviews that seem to rave about the IQ of the 6D... how it is second only to the 5DIII and 1DX... and then conclude that they are somewhat disappointed with it. I don't get it. It's light, it has GPS, wifi, plenty of megapixels (at least for me), and seems like it has AMAZING ISO performance. Not to mention all of its full frame goodness compared to croppers.
Alright, enough rambling... Get the 6D.