I’ve seen a recurring question pop up on the dpreview forums: how much sharper is the IS version of the 70-200mm f/4 lens vs the non-IS version? The answer: On the 5D Mark II the difference isn’t noticeable in the center. On the 18MP crop bodies (7D/T2i/T3i/60D), the difference is noticeable, as is typically the case when evaluating different classes of lenses on higher pixel density cameras.
All samples were manually focused in Live View, shot raw and processed with default settings in LR3. When you click through the images you may need to click a second time to get your browser to show you the full 100% view.