Google has added to its Analytics functions with a Site Speed report to measure page load times.
The report provides detail on a number of levels including average page load time, pageviews, page load sample, bounce rate and exit rate.
The Google Analytics page has this to say about the new functionality:
"With this report, you can see which pages load the fastest and which ones are slower. You can also analyse your overall site speed along other important dimensions in order to learn how your site speed relates to a variety of factors. For example, you can view your site speed across the following categories: