If you didn't notice Google quietly just turned on AJAX search results.
What's AJAX'ing search result pages do?
Why does this matter?
Money money moooooney. Site speed is a huge deal for search engines. Speeding up your results usually means more searches. Which also means more ad clicks, bing bing :).
I have a feeling this was in response to Bing being faster than Google when Bing launched. At least we know Google is on it's toes. I'm still a share holder.
Full disclosure: I worked at Google as a software engineer on AdSense from 2003-2007.