Earlier today, I noticed that my Google results were centered in the middle of the page. This evening, I spotted that you don't even need to hit the 'Search' button anymore - Google updates the results for you while you're typing.
I recorded this quick video to show the SERPs page changing as I amend my query.
Has anyone else seen this yet? It's a testament to the speed of not just Google, but also broadband internet and web browers!
Update: Sources including the Google Operating System blog have referred to this as Google 'streaming' the search results. Indeed, you can see in the video that they offer a link to 'Turn off streaming.'
Further update: Google has launched the product I demoed in this video, under the name Google Instant; this will be rolled out to people over the next few days.
(NB: Cheesy music added because I wanted to try out YouTube's audio-swap feature. The screen capture was recorded using Screentoaster, which I've never used before, but was pretty awesome.)