a post on the Google Mac Blog reads.
The app, which quickly installs on your machine and comes up anytime you double-click the command button is similar to the quick search box included with Google desktop. But as Google notes, it's more similar to the Google Mobile App for the iPhone (minus the whole voice search thing). But this search box is more experimental, using components like contextual search, actions and extensibility.
I've tested it out, and it seems to work fairly well -- a bit faster than Apple's own Spotlight search feature, but with results that aren't nearly as robust from your computer. Still, Google's search box includes web results, which people no doubt spend more time looking for than files on their computers.
You can also easily set it to search within specific areas via a drop down menu. For example, if you want to search Wikipedia articles or YouTube videos only, you can do that tpp.
Perhaps this is Google's answer to Apple's supposed "search engine," but I still believe, if anything, that will be more of a search mechanism across various pieces of Apple hardware you own -- like a computer and the iPhone.
You can find the Google Quick Search Box on its Google Code page.