I rarely use the native email clients from Android and iPhone. Gmail’s mobile web app has a better interface and it’s easier to use than those applications, but there are some limitations that force you to switch to the native apps: you can’t attach files and there’s no support for notifications. Until mobile browsers add support for these features and integrate with the operating system, native apps will continue to be more powerful.
The latest version of Google Mobile App for iPhone solves one of these issues by adding push notifications for Gmail and Google Calendar. You no longer have to use Google Sync to get instant notifications when you receive an email message or an event is about to occur.
I tried to update to Google Mobile App 0.6 in the App Store, but it seems that the new version is not yet available for everyone.