I'm not sure whether it has been officially launched yet - it does work, I have used it, however not all sets are fitted, which leads me to question whether it is fully up and running. As a result, as far I see, it has not yet been launched with a fanfare, although FGW are happy to say that on some trains it is available and will be increasingly so.
I'm not very technical, so i'm wondering whether in some cases the equipment is there but no actual wi-fi signal.