Techradar posted a review on the Adobe Photoshop CS5 iPad apps
Photoshop is frequently used not just for photo retouching, but as a tool to create artwork from scratch.Hands on: Adobe Photoshop CS5 iPad apps review
Doing so with a mouse, or even with a graphics tablet, removes the artist from the process by having to use a separate tool to draw with: how much better it would be if we could just paint straight onto a multi-touch screen, such as the Apple iPad.