What’s so good about Google Mobile for iPhone is the way it presents the different services on the small screen of your iPhone. It practically mimics the same interface as when you're using those services on a regular web browser. Most, if not all of the features on those Google services are in their mobile counterpart.
The first time you fire up the app, you will be presented with the main screen - and guess what the main screen contains? What else but Google Search. What’s interesting about Google mobile search is that it doesn’t only allow you to search the web but your iPhone as well. So, you can search for contacts, telephone number, email address.

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To search your
iPhone you can select to include only your contacts, previous search you did or search suggestions. You can set this up at the “Settings” menu.
You can also set which of the menus you would like to be your default start screen - either Apps, Search or Search with Keyboard.
The app also lets you do voice search. However, according to the app’s disclaimer, voice search only works in English and best for North American English accents. Although I tried using it and got a pretty accurate result. I don’t know, maybe I have an American accent.
One last feature of Google Mobile Search is the safe search feature. It actually allows you to set the security features of the app. You can turn off this feature or put it in a moderate or strict level setting.