How it works: Enable Spaces by clicking its icon in the Dock, then create as many different desktops as you want and fill them with the apps you need to have open-- one for work, another for personal stuff, a third for miscellaneous. Or maybe one workspace for communication where you'll park Mail.app, Twitter, Facebook, and Adium; and another space to hold the things you need for the Keynote presentation you're working on: iPhoto, Text Edit, and Skitch.
Switch easily from one workspace to another with the arrow keys, drag and drop apps from one workspace to another, add more Spaces, and assign apps to always open in a specific Space. There are tons of ways to make Spaces work for you and make your desktop, er, desktops look and behave just the way you want.
Who will use it: Multi-taskers and people who like to have dozens of apps open at once.
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