One new behavior has to do with message actions. To-date, the message actions have been stuck up at the top of the email in the header information. Now, Google says the message actions will float near the top of the screen even as users read through their emails. The main benefit here is that users can now skip scrolling back to the top of an email to star it. (What would we do without Google's obsessive need to speed things up?)
Next up is better treatment of long message threads. Message threads are easy to handle in the browser-based version of Gmail, but not so much on Android handsets. From now on, users can tap "Show quoted text" to open up the previous email in the thread.
Last but not least, Google says that Gmail on Android handsets supports a limited version of Priority Inbox. Those who have enabled Priority Inbox in their desktop email will see "important" messages flagged, and users can even set a shortcut to their home screen for faster access to "important" emails.
Beyond the specifics of the update itself, however, this marks a major shift for Google and Android.
This is the first time that a major part of the Android system has been updated outside of a full operating system update (to Android 2.1 Eclair, Android 2.2 Froyo, etc.) This means as Google moves forward in developing new features for Android's core systems, users won't have to wait for major OS updates to get them. They'll be able to download the updated application by itself, instead.
Google had previously hinted that this was coming, and the change in update strategy should make long waits for new Android version updates less painful, as the best stuff will be available to more people sooner.
Of course, that doesn't mean every Android handset out there gets this new Gmail application. Google notes that Android 2.2 Froyo is required. The new Gmail application is a free download from the Android Market