Site speed is important from a usability standpoint. If you’ve got a Flash-heavy site, or large images, the bounce rate tends to go up, given that people are, by nature, impatient. So, for Google to announce that they’re taking page load speed into account is no surprise.

I’ve said many, many times before that the ultimate goal of Google is to see the web as a real person does, and rank accordingly. They’re getting quicker and better at it. People need information and want data quickly. They want it to be updated and as efficient to access as possible. Attention spans are simply shrinking, and unlikely the surfer will stay very long if the page takes forever to load.

Google’s Webmaster Tools has a great Site Performance tool that highlights possible issues on the page, and gives some detailed information on the issue. You could also install the Page Speed plugin for Firefox to study site speed problems.