Did MAN-AYT-MAN on short-haul 767s earlier this month.
On the outbound, G-OBYF, no IFE whatsoever - the screens just showed a screensaver the whole way and nothing happened when you tried to use it.
On the return, G-OBYH, the system partially worked - map, interactive games and a couple of other bits worked, but no video or audio.
So, on short-haul, you might get a little bit of entertainment out of it. Spending about 3 hours playing poker made the flight pass much quicker! I don't know the reason for not having it on our outbound - we weren't expecting anything so didn't ask.
As an aside, I feel sorry for the passengers who ended up on one of the short-haul 767s over the Atlantic (a few posts above) - the seats are VERY narrow. 4 hours was just about ok but I wouldn't want to spend 10-11 hours in one.