First of all, yes I do realise that Ubuntu Touch is not officially supported for Galaxy S3 and is ported by 3rd party.
So, yesterday I was browsing web, to find how far Ubuntu has gone with their Touch. Looks good for nexus devices atleast in videos, they I started wondering, maybe it is ported to my Galaxy SIII? Found out that it is partially with lot of bugs, but I still wanted to try it out. Found OS image and 4 step Instalation guide under ubuntu wiki, with information about development status and bugs.
So I made backup for my PA3+ ROM and flashed over Ubuntu touch. So far so good.
Turned on my phone, boot time was almost as fast as on my laptop with SSD, near 5 seconds, familiar Unity like screen was greeting me and smile appeared on my face.
Problems started when I actually begun using it. First thing I wanted to try were call someone, but instead while trying to figure out how to do that I connected to WiFi (that worked) and opened facebook (quick access icon in toolbar) Facebook thought I was from iPhone and suggested to redirect me to app store to download app, but instead I got my first force restart with pulling out battery. Phone was just not responding.
Restarted phone and this time I acctualy tried to call. Opening catalog app was unlucky, every time white screen and phone isn't responding. Pretty much everything lead to whitescreen and force restart.
After 20 minutes and complete dissapointment I had to restore my backup.
Bright side is: atleast there is some progress and hopefully lot more devices will support Ubuntu Touch in near future.
Here you can read more about devices https://wiki.ubuntu.com/Touch/Devices
And here s xda-developers thread http://forum.xda-developers.com/showthread.php?t=2315397
And here is the video which encouraged me to try it out http://www.youtube.com/watch?v=qKqQ3JyPIDA