Google now using site speed in Web search ranking

Google using site speed in Web search ranking (April 09, 2010)
http://googlewebmastercentral.blogspot.com/2010/04/using-site-speed-in-web-search-ranking.html

...today we're including a new signal in our search ranking algorithms: site speed. Site speed reflects how quickly a website responds to web requests.

Speeding up websites is important — not just to site owners, but to all Internet users. Faster sites create happy users and we've seen in our internal studies that when a site responds slowly, visitors spend less time there.

Personally, I think website speed will be a very small factor unless a website loads unusually slowly. You can use the tools that they list to check your website's speed.