My initial feelings have really not changed-
The lens is a work of art, it's pin sharp, fast, and the IS (image stabilization) is top-notch. But it's HEAVY. I took it out with me to the woods walking the dog today, and by the end I was really wishing I had a more padded strap on it. And on Sunday, taking pictures of the fams doing Christmas, I took less pictures than I usually would have coz my arms got tired! Don't get me wrong- it's a fantastic lens, but my 70-200 f/4 non-IS is less than half the weight and a quarter of the price, and it's almost as sharp and a lot easier to tote around, and the lack of IS is slightly made up for because your arms aren't shaking under the weight of it ;) At some point I would love to try the two Canon 70-200s that fall between these- the f/4 IS and the f/2.8 non-IS.
The 5D body though is another matter- that I must have! Everyone says the 6D is as good in low light as it has the same full-frame sensor, and that is probably true- but the focusing system in the 5D is much closer to the one in the 7DmkII (11 focus points in the 6D vs 61 in the 5DmkIII and 65 in the 7DmkII) and in action the 5DmkIII blows the 6D out of the water! It is also bigger and heavier (by about 1/3 of a pound), but it actually feels much better in my large-ish hands. I am going to spend a little time deciding which camera body to keep (7DmkII or 6D) and which to sell, along with which lenses I could also sell so I can get one.
Anyhow- here are a few last pics from late this afternoon on an overcast day in the woods with the 5D and it's monster lens friend...