Rand Fish from the Pubcon conference:
Web Page Load Time can Positively Influence Rankings
Maile Ohye actually mentioned this at SMX East in New York, but Matt Cutts repeated it again today. In a nutshell – while slow page load times won’t negatively impact your rankings, fast load times may have a positive effect.. In addition, fast loading pages are, in my opinion, considerably more likely to earn links, retweets and other forms of sharing than their slow-loading peers.