As someone that thought this very same thing and did something about it (sold all my Canon gear and bought a D600) I can shed some light my view:
1. The 6D is woefully overpriced compared to the D600 on paper. No one has used a 6D yet, so we don't yet know whether or not it is "worth" $2100... but you certainly get more "features" for your dollar with the D600. This one won't be settled until the 6D comes out.
2. D600 AF Spread. It is definitely less than the 7D I sold to get it... and it _is_ inconvenient. However! The D600 AF is REALLY freaking good. It is insanely fast (nearly instant with the 24-70G) and very accurate, even in low light. Also: yes, the points are really close together, but in my limited experience that does help with tracking... ie, the camera never loses "sight" of the target between AF points (although... it _does_ lose it if the target leaves the center of the frame!). Finally: I really _like_ the tiny AF points... they are very easy to stick right on an eyeball to nail a portrait...
3. High ISO: I think it's _really_ good. See my thread here: http://www.canonrumors.com/forum/index.php?topic=10335.0
I haven't shot with a 5DMkIII or 1DX so I can't compare... but I am really happy with it!
4. I really think people need to quit comparing the 6D and D600. The proper comparison is 5DMkIII and D600. Even though ~$1300 separates them... they are MUCH closer to each other than the 6D and D600. Here's how I see it:
5DMkIII and 24-70II: ~$6000
D600 and 24-70G: ~$4000
D600, 24-70G AND the awesome 14-24: ~$6000 (Perfect Landscape Kit!)
Overall, at this point - I don't think we can say much about the 6D. We're going to have to see it in action.
However, for everyone out there that is underwhelmed by the 6D specs... I can confidently say that the D600 is a great machine. The IQ is absolutely awesome and the machine just flat _works_. I'm really loving it.
Absolutely zero regrets at this point...