I've had SketchBook Pro for the Mac for a few years now. I bought it before it was acquired by Autodesk from Alias, mostly for art work, but also to experiment with it as a tool for interface sketching. But while I wanted to use it more, I find myself falling back on paper and pencil almost all of the time. Autodesk recently released iPhone versions of the app (1 version is free, and the full version is $2.99) and I think it might actually be more useful to me than the desktop version.
I've been playing around with the app as a possible tool for user interface sketching, and am impressed with what I could do with the limited canvas of the iPhone. Right now it feels a little limited for my use. But I am more excited at the opportunities this might provide in the future if any of the Apple Tablet rumors come true.
Using SketchBook Mobile on the iPhone is pretty tough. You can see in the demo video above that the user is drawing with his fingernails and working zoomed in much of the time, rather than drawing at 100%. Zooming is easy with the pinch gesture, but having to constantly zoom in and out is a little tedious when you need to back up and see the whole of your drawing. Using stubby finger tips is also hard, but you can get around that largely by using a stylus.
The interface feels exactly like the SketchBook Pro desktop app. The radial menus are easy access, and thoughtful shortcuts for clearing and undo are provided with double clicks. Panning is a 2 finger gesture, and zooming is familiar using the pinch gesture. The iPhone version actually uses the same paint engine as SketchBook Pro, so it uses the same drawing tools, and they feel and look the same. The same interfaces for layers, color picking, and brush creation are also offered. Saving and sharing is also possible, either by saving to your photo library, or exporting as PNG to email.
Where the small iPhone canvas feels restrictive in SketchBook Mobile, I imagine that a 10" touch screen canvas will feel absolutely perfect. I'm currently using a process for recording and reviewing sketches where I sketch in either of my small 8" or 5" notebooks, snap a photo with my iPhone, and then post via email to our company's CMS, where I can annotate and people can review and comment. But I would be more than willing to try to sketch directly in SketchBook and post those drawings rather than having to jump through the hoops I do now, few as they are.
As you can tell, I'm sort of excited by the idea, and I'm feeling like there are enough indicators that the rumors for the Apple Tablet may be justified. Keeping my fingers crossed.