I updated my xbmc .apk from 12 to 12.3 with no problems just last week. I was waiting for Matricom to release their "special" version of the XBMC apk...but I'll grow old waiting for them to push any updates out. So I did it myself...and am very happy I did. You can do it severals ways, but the following two are the easiest:
1. On your computer, download the Android 12.3 .apk file to the SD card (or thumb drive) that is usually in your G-box. Put SD card back in your G-Box...then use File Manager to locate file...then double click on the 12.3 apk and install. Exit out of XBMC, then reboot.
*This is all done before you even open the XBMC app, in the main menu*
2. On your G-Box...browse to the XBMC site and download the Android 12.3 .apk to your G-Box and install from there. I did it this way and it took less than 3 minutes.
**** Updating from 12.0 to 12.3 did not wipe out my XBMC setup, however I would download the "XBMC Backup" add-on that allows you to backup your entire setup and save it on your SD card. This way...if something goes wrong, you can always restore your XBMC setup using the backup add on.
I was anticipating the update would completely wipe out my XBMC setup based solely on the experience I had when Matricom pushed out their incremental update for the MX2 firmware...which totally wiped not only XBMC, but the entire box to like-new. That sucked!!!!
Go for it...you won't regret it. The link for the MX2 is below
http://mirrors.xbmc.org/releases/android...bi-v7a.apk
