The first three Adobe Photoshop iPad apps are now available at the app store. I've been using them for a while (full review to come later) and they are really really good.
The price is right on the mark too: Adobe Eazel, my favorite both because of the media simulation and the five finger interface, comes for $5. That works as a standalone paint application and connects to Photoshop, sending images that get automagically scaled to whatever resolution you want.
Adobe Color, which will mostly get used by designers to create color themes on the go, is available for $3. Adobe Nav, which allows you to control Photoshop files and tools from the iPad, is available for $2. I'm getting them all.