Google uses page load speed as one of the signals in their ranking algorithm. While they previously provided an indicator of your sites speed in Webmaster tools, but it wasn’t on-going (they only sampled periodically).
With this announcement, Google has added Site Speed To Google Analytics.
I think page load speed is something everyone should be monitoring, especially if you’re in a share hosting environment (like most of my customers). It will also be beneficial in identifying slower pagers on you site. Monitoring page speed does require a change to your Google Analytics tracking code, I recommend everyone update this ASAP. I am sure the Joomla and WordPress plug-ins will add this feature shortly, but you may want to check to be sure the plug-ins you’re using support this feature.
5/10/2011 Update: Google Analytics for WordPress, by Joost de Valk now includes this feature by default.