Posted by philastokes
Prior to Mavericks, a quick and easy way to get the ‘Shutdown’ dialog box (above) was just to press and release the power button. If you try that now in Mavericks, all you’ll do is put your computer to sleep!
Don’t worry, the old functionality is still there, it’s just that Mavericks has re-programmed the power button slightly. Here’s what it now does:
Press and release: put the Mac to sleep.
Press and release with Control ^ key: display the ‘Shutdown’ dialog box.
Press and hold (release after 3 seconds): display the ‘Shutdown’ dialog box.
Press and hold (10 seconds): instant power off (aka “hard shutdown”).