Users of Google Analytics will be able to determine which landing pages are slowest, which campaigns correspond to faster page loads overall, how page load times vary across geographies, and the loading time difference in different browsers.
In order to see the data in the Site Speed report, Google Analytics users will need to make a change to their tracking code (just insert the bold line as seen in the code below). Once the updated tracking code has been verified the report should be available within a few hours in the GA account.
Google mentioned that they will only use a small smaple of pageviews to calculate the page load time.