It arrived! It was super windy here today, and I didn't have much time to wander about, but I'm pretty happy with this from my first hour with the lens:
Canon 5DmkIII | Canon 70-300L | 1/100s | f/9.0 | ISO200 | 300mm
My refurb unit appears to be basically pristine. No cosmetic or apparent image quality flaws, just the tiniest wiggle in the focusing ring (and only forward and back, no play in terms of turning it). I'm absolutely loving the IS. I know the focusing speed should be comparable to my 70-200 f4L or the 135mm f2L, but I'm not used to that smooth, non-jittery image in the view finder, which makes the whole experience feel more immediate. I can't wait to get out with it more.