Is page load speed (site speed) a factor in Google PageRank?

Officially, the speed of your site isn't a critical factor. BUT, here is (Google's bigwig) Matt Cutts' comment on the issue: "Historically, we haven't had to use it in our search rankings, but a lot of people within Google think that the web should be fast. It should be a good experience, and so it's sort of fair to say that if you're a fast site, maybe you should get a little bit of a bonus. If you really have an awfully slow site, then maybe users don't want that as much."

So, err on the side of caution and streamline your site to have it an its optimal load speed- not too many images, no large images, minimal or no Flash, etc. The user experience is still paramount to Google's official stance, and no one wants to wait for minutes while a site loads.