Matt Cutts wrote:In fact, if you read the official blog post, you’ll notice that the current implementation mentions that fewer than 1% of search queries will change as a result of incorporating site speed into our ranking. That means that even fewer search results are affected, since the average search query is returning 10 or so search results on each page. So please don’t worry that the effect of this change will be huge. In fact, I believe the official blog post mentioned that “We launched this change a few weeks back after rigorous testing.” The fact that not too many people noticed the change is another reason not to stress out disproportionately over this change.