Upload & Sell: Off
I had one that I just recently sold to get the Canon 300 2.8 (non-is).
For the price, it's a great deal. It's quite sharp, but not extremely sharp, and oftentimes there was the occasional chromatic abberation more than I was expecting (and I did a microadjust of I believe +15)
For football, the focus was good when the subject was fairly far away, but if there was ever a quick approach towards the camera (I was using a 1D4), than it couldn't keep up.
Here is a shot with a 5d2 of Joe Biden when I was covering a lot of elections: http://www.flickr.com/photos/srontgorrth/8101483273/sizes/o/in/set-72157631802525870/
Not ultra sharp, but sharp enough for most. You can see some purple fringing on his left wrist.
Here's another sample, using a 1D3 at f3.2, ISO 2000, and 1/400 (on a monopod): http://www.flickr.com/photos/srontgorrth/8123119480/sizes/o/in/set-72157631802525870/
I bought a Kenko 1.4x teleconverter but the results with it were extremely lackluster, though they didn't fare well on my 70-200 2.8 either. I think it was more the TC than the lens.
Bokeh wise, the lens was/ is excellent. And as mentioned, one of the reasons I got it over the 120-300 was because the zoom wasn't really 300mm.
So in short, if you're buying a used copy, it's a hell of a deal, and if anything, buy one and use it while you save up for the Canon copy, which is what I did (the 300 non-is arrives next week!).