Typically, if you go to Google.com, you can type in a query and press search. But these users are seeing an auto-complete feature that you would typically only see on Google Suggest. Here is a screen capture of how it may look:
Can this be coming to the main Google.com search results? Possibly. Yahoo does it by default with search assist and they love it. Ask.com does it also. So if it works, why not port it over the the mainstream?
Forum discussion at WebmasterWorld.