Does the mail app in iPhones still use POP for Gmail? Or is it updated to use IMAP?
If you pick the Gmail option when setting up your account, it will use IMAP. However, if you set it up as descibed here, it uses ActiveSync. Doing it this way gives you push notification as well as contact and calendar sync.
The "Gmail" option for iPhone mail configuration has always used IMAP. I would, however, recommend configuring it as an Exchange account, especially now that iOS officially supports multiple Exchange accounts (previously the domain of jailbreakers only). Doing so will push emails, contacts, and calendars directly to the phone, though you won't be able to sync Notes like you can when using the "Gmail" option.