So it's official. You will now be penalized by Google if your website underperforms in terms of speed. While the impact should be minimal right now, there is no doubt that this can and likely will become a major differentiator for search ranking down the line. Faster sites not only mean happier users and a happier internet, they also mean less overhead time for GoogleBot as it scans sites that perform more quickly, so it's in Google's best interest to make things go faster all over the internet.
http://googlewebmastercentral.blogspot.com/2010/04/using-site-speed-in-web-search-ranking.html
This implies a couple of things for your website and your ability to acquire a good search ranking score.
Excellent Search Engine Optimization techniques are no longer good enough. You must also keep a sharp eye on your site performance. Make sure that you are configured for maximum optimization including output caching, compressing static web content, and keeping your technology stack up to date. The article suggests several measuring tools for tracking the speed of your website. In addition, you might want to turn a critical eye to pages that are getting crawled, determine how relevant they are to your site SEO strategy, and then put a "no follow" on links to less relevant pages that do not perform well but are getting crawled and potentially damaging your performance rank.
Be aware of third party tracking tools that might damage your performance rank. This is true of not only any crawlers should they choose to track page speed based on all of the resources your page requires, but its also true if you are using services like Nagios or Keynote to track and alert you if your pages are slow. While the user might not have any real problem in the browser waiting for a DoubleClick ad to load up, your performance metrics and any bot performance tracking might be harmed.
This also could potentially impact how you build your SEO content. There are several approaches to providing SEO content to crawlers. One is to dynamically respond to a query and build a response with some sort of code. Another is to build out a bunch of static html pages ahead of time in response to any possible SEO requests. There are others, but the larger issue is it becomes even more important to weigh performance over ease of implementation or reuse of existing infrastructure.
I can attest from my personal experience that site performance is directly tied to site usage. On past sites that I have worked on, performance improvements have almost always been followed by spikes in site metrics such as page views and ecommerce sales. However, I am concerned with how this requirement by Google un-levels the playing field in regards to SEO rank. Before, if you had great content, that was good enough. But now, if you can't get your site to perform up to Google's standards, you could be in trouble. I have to wonder what that means for small lightweight shops who have the resources to address their content but don't have the resources to pay for high end servers or qualified programmers to make their site work as fast as possible.