Gmail for iOS got a big improvement today, adding support for Notification Center and push messages. You can also send messages from an alternate address if it was enabled in your Gmail account.
Also, the login process is improved to allow you to stay logged in for length of time. Previously users would be kicked out and have to log back in again.
Software engineer Jason Parachoniak announced the changes on the Official Gmail Blog. While multiple account support is not yet offered, it is promised to be forthcoming.
Those still not satisfied with the native mail app on iOS have also flocked to Sparrow, which has been busily adding features. While push is not yet supported, labels and conversations sync with one’s Gmail account.
Source: Official Gmail Blog