The new Demographics & Interests reports in Google Analytics can be useful and are very easy to configure.
You need only to enable Display Advertiser Support in your tracking code setup to include the following DoubleClick reference (and make sure, of course, to copy to the code to your site):
ga.src = ('https:' == document.location.protocol ? 'https://' : 'http://') + 'stats.g.doubleclick.net/dc.js';
Note that the Demographics reports are not scheduled to be available in Google Analytics Universal till sometime in Q1 2014, so if you want to begin using the Demographics reports (or are already using them), you might considering delaying your migration to Universal just for a while.
More details about the Demographics & Interests reports are available in the complete overview.