Google Adds Load Time to Quality Score Equation

Not only will load time issues cause site abandonment, a quality score penalty that started in February could hamper search marketing campaigns for sites with load time problems.

Probably the best article on this is at Search Engine Roundtable (see included link) offers these tips for avoiding load time penalties:
* Use fewer redirects.
* Reduce the page size by using fewer, smaller, and more highly- compressed images.
* Do not use interstitial pages. * Minimize the use of iframes on your landing page.
* Contact your webmaster or webhosting provider to discuss other ways of improving your website's load time."

The article also says your "load time will receive one of two grades. If it's graded This page loads slowly, your landing page quality and Quality Score will be negatively affected. If it's graded No problems found, your landing page quality and Quality Score will not be affected."”