Apple’s launch Wednesday of its next-generation OS, Mac OS X Lion, meant the Cupertino, Calif.-based company was rolling out a series of big-time improvements to its computing experience. Here’s a look at the top seven you should know.

Out: CDs and DVDs with upgrade software or a complete OS.

In: the Mac App Store’s downloadable upgrade.

For $29.99, Lion was a direct download and installed in less than 90 minutes on supported systems.

Apple’s new Launchpad feature, which is aimed at making it easier to navigate to specific apps and applications, works as advertised. Importantly, it creates the same look and feel as you’d get on an iPad or iPad 2 – which Apple wants to provide a seamless feel between the top products in its lineup.

This caused some consternation among Mac OS X veterans because Apple has essentially reversed the scrolling motion on the desktop. However, it’s more like iPad navigation. We found it simple to adjust, and Apple provides an option in system preferences to restore it to the classic scrolling gestures.

This is a significant departure for the Mac, and one that’s needed now more than ever. With a single click, it’s possible to expand an app to use the entire display. Some developers have taken advantage of this feature; Microsoft Office 2011 for Mac provides this nice ribbon for Word in Full Screen mode, which we thought was somewhat nifty.

Apple now makes it easy to stop losing track of how many apps you’ve got open at any one time, with a one-click view of everything you have running. Mission Control also supports its Workspaces feature, so you never have to let your system get away from you during the work day.

Apple has given its e-mail a facelift to make it look more like the mail app on its iPads and iPhones. It’s easier to navigate and view than previous versions, and will provide a consistent look and feel across its platforms.

This is big: Apple has given its Calendar a new look and feel, and provides much better and much more intuitive integration with Google Calendars. It also provides a full-year view, as well as color-differentiating different calendars that you import into iCal, either from Exchange or other services.