To experience Google's instant results, you'll have to enable the feature by tapping the "turn on" link on the Google.com homepage.
The mobile release of Google Instant is still in beta, so it's not bug-free. Results for the first prediction will appear immediately, and clicking on other predictions immediately displays those results. And, since mobile browsers can be fickle, you are able to turn off Google Instant by tapping the "turn off" link at any time. Check out Google's blog post for more on Google Instant for mobile devices, including a helpful instructional video.