If you're a seasoned Gmail user, you're probably well aware that Google's email is available via IMAP for use with your iPhone. Of course, in previous versions of the iPhone firmware, the all-in-one Gmail configuration option was for the (very different) POP protocol: Gmail didn't enable IMAP until after the launch of the iPhone.
If you know your IMAP from your SMTP, then you're probably already aware of why this is neat -- and also a curse over the previous POP system, if you don't take careful note of how the different protocols behave. Because IMAP actually keeps all your folders in sync with your server-side mailbox at Google, any changes you make to your mail on 1.1.3 will now also be reflected on the Gmail server. This means when you delete that message on your iPhone, in 1.1.2 it would still be archived on the Gmail server; with 1.1.3 and IMAP it now hits the master trash can and will be deleted after 30 days under Gmail's trash can rules. You have been warned!