Official Gmail Blog: New Gmail for the iPhone

Google launched the new version of Gmail for Mobile on your iPhone which includes powerful set of web development techniques that make web pages to load much faster.

it also two most requested features: Prue-fetching and auto-complete.

it will give you the facility of virtual keyboard

Gmail will automatically preload all recent messages for you, when you use Google on your iPhone.

"how to do it"
1.from you iPhone visit
2. hit Gmail button
3.and sign in