CM10.1 is an open source replacement ROM for the Android phones and tablets. It looks and feel very much like stock Android and is much faster than the stock factory firmware. Cyanogen Mod 10.1, popularly known as CM10.1 is out for the Samsung Galaxy Tab 8.9 and almost everything is working, including GSM calls. Of course, to flash it, you must have Clock Work Mod recovery installed for the Tab 8.9.
List of working things.
3G (including GSM calls)
WLAN
Audio
Rotation
Storage
Cameras (both)
Keyboard dock
You can get the latest build from these links – P7300 [link] and P7310 [link]
The only that is not said to be reportedly working is the HDMI which also does not work on CyanogenMod build for the Galaxy Tab Plus tablet.