Just acquired this lens and really impressed with the images from it. Compared to my 24-70L the images just seem to ooze quality. It's a combination of factors, but the end result is amazing. I was also considering the 70-200 2.8 IS II but I'm so glad I went with this one now.
You can see some test images on my <a href="http://sarahmcdonnell.co.uk">wedding photography blog</a>.