Here's report of a pretty adventurous test, spotted by Rob Ousbey who was sharp enough to grab a video screen capture: Live updating Google results
Typing into the search box while on a results page, the actual SERP keeps getting updated, giving you a preview of the #1 Search Sugggestion. I haven't been able to see this on any browser. But I imagine getting served the text depends on a very fast connection, so that all the AJAX can work. Anyone else see it?