On Friday Google engineers announced that Google will consider site speed as part of the formula it uses to calculate search engine rankings. Google's general philosophy is faster is better but Google says site speed is just one of the many factors it uses to determine search engine ranking.
The good news is... sites built and hosted with WebStarts are on a super fast premium network. So as long as you don't load up your web pages with large files like over-sized images sites built with WebStarts should see an advantage.