18-55mm II Matches 17-55mm Image Quality, Canon Confirms

Here's a comparison between the 18-55m II and 17-55mm lenses shot, as Canon requested, both on a tripod, no IS and at f8. Canon initially claimed the 17-55mm would beat the 18-55mm II images. After a training and design engineer over the pro slr division reviewed the images, he claimed that they were "essentially the same". That image quality would not improve until you get below 5.6f.

The 18-55mm II images are sharper to my eyes, with CA as expected. Top two images are taken with the 18-55mm, the bottom two with the 17-55mm.