Google has been busy with testing search interfaces this weekend.
A new test spotted by a member at WebmasterWorld claims Google is testing a form of an instant next button in the search results. This is a lot like how Google and Bing handle showing image results with infinite scroll.
The searcher explained in the thread:
When you click on the next page for the SERPs it now displays the following page below the first page, and so on. Still a few bugs though, but should be faster. I guess they may eventually use infinite scroll, like they do for images.
I have not heard of anyone else noticing this weekend but it would not surprise me if Google tried to make loading the next search results faster through loading the results below the top ten results or loading them as you scroll.
Forum discussion at WebmasterWorld.