I'd be interested in the answer to that question as well. As a 60D owner I'm actually surprised at how similar the two cameras seem to be...I recently upgraded from the 60D to the 5DII. They seem very similar in most of the ways that I shoot. A couple ergonomic issues are different, but largely they are the same. For example, the AF seems identical. The metering on my 5DII seems a little more accurate. The key differentiator is the ISO speed and cleaner noise at higher ISOs, which benefits the 5DII (and 6D) substantially. Regardless of how the 6D performance shakes out, you should consider a 5DII upgrade path because the ISO performance is a real upgrade.
Thanks for the insight...interesting. I really do like the 60D- it even exceeded my expectations when I shot some action last week- for having "only 9" AF points I got quite a few keepers.
My only complaint about it, and it's not really a complaint per se as it's a wish - I would like better high ISO performance. There are times that I'm feeling the limits of ISO 3200 (yes, even with an f2.8 lens) and would like to go higher but can't due to the excessive noise levels. Hoping the new 7D II has this, and I can keep the crop factor for my long lenses.
To clarify, any use for a FF camera like the 6D would be mostly travel, walkaround and events. If I chose to go this route, I would almost certainly keep the 60D to get maximum reach out of my telephotos (70-200 2.8 and 70-300). Lens-wise, I have mostly EFs anyway - the only EF-S I have is the 17-55 (but it's one of my most used ones).
I'd like to see how the 6D's AF performs in practice, and whether it is at least on par with the 60D, because it sounds like at least on paper, with the exception of the low-light rating, it's somewhat of a downgrade. Plus, if it's true that FF cameras require more accurate focusing due to more limited DOF, this would seem even more critical...?