I recently had to shoot a group portrait with it in a fairly high contrast situation on my 7D and I spent more time removing fringing than anything else. Barrel distortion is also pretty noticeable but I understand that has been rectified with the IS version.
Oh ok. Yeah I haven't taken more than maybe 200 photo's with the 18-55mm lens. Bought the 70-200 about a week or two after buying the camera.