Here are the features as listed in the Windows Store:
Google Searchbox - Type your search right from the app home screen, so you can find the answers you need more quickly.
Voice Search - Use your microphone to ask Google anything and see the answer instantly.
Image Search - Watch images load into a beautiful full-screen grid. Select images you like or swipe through to see more results.
Search Charm - By installing the Google Search app, you can easily access Google from the Search Charm.
Instant Previews mode - Browse search results without having to visit each page.
View Your Searches - Swipe from the top to see the sites you visited most recently, categorized by keyword.
Google Apps page - Access all your favorite Google products from within the app with just the tap of an icon.
Google Instant - No need to press Enter - see results instantly as you type.
The app can be downloaded from the store, or from Google's GetYourGoogleBack site.