Other than dynamically-related colors, is this much different from designing in Illustrator and exporting to PDF, which I understand is well-supported in iOS and OS X?
Code generation seems to be the selling point. I've never seen wel executed GUI code generation however on any platform. Windows Forms was especially awful...
It looks like to biggest extra is the ability to insert variables into the generated, so you can make e.g. a blue and orange button from the the same output.
Think 'Save As NSView Code' for Illustrator.
Your PDF is going to be resolution independent and end up being used in much the same way as the code, so I'm to sure it's a significant difference.
I do like the automated color derivation though.
Add a parameter or two to the generated code, then you'll see the difference,
Good point, although if you knew what you were doing with PDF ( which is, after all, itself written in a programming language... )
True, but that is clearly impractical within a cocoa program since the PDF handling methods don't provide a mechanism for passing in parameters.