Previously you could just sync your Google contacts and calendars, but now finally it supports Gmail as well, allowing you to be notified instantly when you get a new email. Push Gmail via Google Sync works on the iPhone as well as in Windows Mobile and Symbian.

Update: One thing to note: if you already have an Exchange account on your phone for, say, work, you won't be able to add a second for your personal account. It's never perfect, is it? [Google Mobile Blog via TechCrunch]

All of this was possible before through a smartphone's web browser (and Google Sync has been available on Blackberries for months), but if you were looking to push update your phone to various Google-stored information through the iPhone or Windows Mobile, it was pretty much a read-only experience. Now you can treat Google's calendar and contacts like any push service, updating your phone to the cloud in real time.

And I'm way too excited about this development. [Google Sync via lifehacker]

UPDATE: I'd mentioned that Gmail was included. It is not.