Installation instructions for non-AOSP roms w/ overlay ie Samsung TouchWiz, HTC Sense, Sony (reported to be a working method w/AOSP roms ie CM 9/10, AOKP)
1. download the apk and place it on your sd card
2. use your favorite file explorer and tap the apk (make sure you have “install from unknown sources” enabled in your phone settings)
3. go into your phone’s keyboard settings and enable “Android keyboard”
4. enjoy!
Click Here
Credit: XDA Forums / Android Police
That video above shows a small preview of whats new in Gmail 4.2.
Instruction:
1. Download the apk from HERE.
2. Make a titanium backup of your Gmail App first.
3. If you are have your Gmail app installed in Data/App, Delete them first, if not skip this step. You won’t lose your Gmail data, dont worry
4. Copy the Gmail.apk using any root explorer to System/App.
5. Reboot.
6. Launch the Gmail app, and your Gmail data will be still there.
I have yet to try it myself, so please do this at your OWN caution. Let me know if it does or doesnt work for you,
Credit: XDA forum
Amphitheatrum Flavium MMXI 