After the launch of Google Instant, the biggest challenge was to import the feature to all the hand held devices. It took Google 2 months to roll out the beta version of Google Instant for mobile devices after their announcement in September.
To use this feature, you need to log on to your browser and tap the Google Instant “Turn on” link beneath the search box. It works exactly like you desktop version of Google Instant with live predictions and their relevant searches. Results for the first prediction appear automatically, and tapping on the other predictions will display those results. Pressing the enter key or the search button skips the predictions and will display results for exactly what you’ve typed.
There has been a big improvement in speed when you search. This is because of HTML 5 and AJAX implementation of Mobile that dynamically updates the page.
Reference: Google Blog