In the Navigator screen, the layout and icons for Projects and Categories are too similar (They have more potential for repetition and, therefore, confusion.) so it would be helpful if they were differentiated more from each other.

The Calendar setup is instantly identifiable as are the icons for the Contacts. I've misfiled things within Projects and Categories because they inherently have more overlap and the briefcase versus folder icon both in color and shape look too similar as well as the folder structure.