The Omni Group has released OmniOutliner 4.0.4, with a fix for printing with manual page breaks, a solution for crashes when zooming, corrections to a number of documentation typos, and correct menu options when not running the Pro version. ($49.99 new, free update, 45 MB, release notes)
Option-click to Hide Apps Quickly
This trick has been available in the Mac OS for years, but many people still don't know it. If you have too many windows cluttering up your screen, you can hide specific ones easily as you work. When you're in any application, hold down the Option key and click on another app's window, on the Dock, or in the Finder to switch to that other app and simultaneously hide all the windows in the previously current app.