As 9to5 Mac explains it, the most appealing feature of this iOS, portable version is the ability to swipe through the previews generated by your search query just as you would through Safari's tab feature.
No official announcement was made by Google on this, nor is it available to iPhone 4 or iPad. A limited test roll out seems the most likely explanation, with a full blown all-iOS roll out imminent.
Is the feature live for you, Gizmodo iPhone or iPad owners? [9to5 Mac]