Scotte promises to give us the facts, or most of them:   "Q. As a photographer what is the most compelling reason to consider an upgrade from CS4 to CS5? A. That’s a tough one, because it will be different for different photographers. I think a lot of folks will naturally want it to create HDR images, but I think the built-in masking features (using Refine Edge) is even more compelling for most photographers. Content aware fill is big (and it works amazingly well), but then the Noise Reduction in Camera Raw is just insane, so it’s a tough call to make. Luckily, any one of those is worth the upgrade alone, so if you get all four, this is an easy decision for a lot of photographers."   Link