[Bill Van Hecke]

There are a few nice things about using OmniGraffle instead of Interface Builder to mock up Cocoa interfaces:

- You can drop in a screenshot of an existing interface, and add new elements right on top of it.
- You can turn layers on and off to see how different elements would look on the same window.
- You can use the drawing tools to mock up custom controls that aren't available by default in Interface Builder.
- You can store lots of different mockups for one project as multiple canvases in one file.