Here are a few reasons: GIMP starts up so fast I don't need to make an espresso, thus reducing caffeine consumption. Save-as-JPEG can mimic the quality parameters of any existing JPEG to reduce artifacting. Menu picks are more accessible than CS2, for instance Levels and Curves are at first level. Easier to zoom up and down and shrink/expand the window to fit. Most dialogs have fine-grained up/down control over numeric values. Curves window includes Levels histogram. Levels window has exponential view and can be stretched (see below). I'm not going to list GIMP's drawbacks, although I know what they are. We'll probably upgrade to CS4 after Xmas when we have better cash flow. Nothing about CS3 seemed exciting, but CS4 starts up faster and has, umm... what does it have?