If you haven't yet manually updated Gmail to the redesigned 4.5 release, it's rolling out on a wide basis this morning to users in numerous countries. If you can't see the update on your device, try forcing the install from the web version of the Play Store, here.
The new version of Gmail for Android includes support for the all-new inbox tabs from the desktop Gmail, along with a totally revamped slideout navigation bar. Learn more about the update and the new inbox experience here. In the meantime, head to the Play Store and get that update! As a technical note, this is the same version we provided as a download earlier this week, so don't fret if you flashed manually - you're up to date.
If you're still not seeing the update, you can manually download the APK right here.