 The "Back to the Mac" event also included a preview of Apple's forthcoming Mac OS X Lion operating system, to be released in mid-2011.
<clarity>  The "Back to the Mac" event also included a preview of Apple's forthcoming Mac OS X Lion operating system, to be released in mid-2011.
 The "Back to the Mac" event also included a preview of Apple's forthcoming operating system, to be released in mid-2011.