Several of the core apps can now be run in full-screen mode so you can work (or play) without distractions. Apple says third-party developers will be able to add full-screen functionality to their apps as well.
Mission Control takes the best things about Spaces and Expose and ties them together in one useful screen. With a simple three-finger swipe upward, you'll have everything running on your Mac at your fingertips.
Acting as a set of temporary bookmarks, the Reading List will make managing your daily reading a snap. Just click the plus sign to the left of the address bar or Shift-click a link to add it to your Reading List. When you're finished with today's reading, you can save stories for later or clear it out.
Launchpad brings the iOS app experience to Mac OS X Lion. We're not sold that it's the best way to navigate your apps, but the unifying design aesthetic will probably make it easier to switch for those whose only experience with Apple is through the iPhone.
Apple's Mail App received a lot of attention in this update, adding excellent search tools, a layout like the iPad Mail app, and conversation views. We think this will be one of the favorite upgrades among Mac users.
When doing a search in Mail, you can select from suggested results to make Search Tokens (gray buttons). From there you can add more tokens and drill down to exactly the search criteria you want. This feature will be useful for zeroing in on messages you can only remember specific parts about (such as a last name, an obscure subject, or even a general time frame).
The new local sharing feature in Mac OS X Lion lets you view all nearby users so you can quickly drag and drop a file to send. With AirDrop you no longer have to navigate through menus or compose an e-mail when you just want to send a file.
Introduced in an update to Snow Leopard, the Mac App Store gives you the same ease of use for Mac apps that you get in the App Store for iPhone apps. It's also the only way you can Download Mac OS X Lion, so you'll need to upgrade to Snow Leopard in order to get Lion.