Hey...congrats on the new glass. I've been very impressed with the Sports version. But, I've paid attention as the reviews have rolled in and, honestly, the gap between the two seems very minor. In some ways, because of cost, size and weight, the "C" may be the better option for a lot of people.

As an FYI, I find the images useable at 600 f/6.3, but, at least with the "S," sharpen up nicely at f/8.