In Google Analytics, you can monitor your site speed and get a decent overview of what pages are contributing positively and negatively to site speed. The problem with page load time metric is that it’s an average based on a sample. You can modify the sample rate with setSiteSpeedSampleRate(), but for me that’s not bloody well good enough.
(UPDATE 28.3.2014: This post is still valid, but an implementation with User Timings is a much smarter way to measure actual page load time.
