Firstly I wold not recommend purchasing this lens online, and here's why: Personally, I had to try two copies at the photo store. Once I got home and put the lens to work I noticed that I got a sharp one, but the autofocus was hunting. The next day I went back to the store, tested two more and finally got the good one. That should not happen, Canon, with a lens worth 1069 EUR ! (I'm from Europe).
Secondly, once you get the right copy, you'll be impressed by the picture quality and color rendition. Still, not as tack sharp as my 70-200 f4 IS, but very close to that. Excellent build, I'm not complaining about the weight because I know that this comes with all good L lenses. Love the hood and the fact that although the lens extends while zooming out, it does not "pump" air inside the camera body (sensor end of the lens is sealed).