I just got off of AC 857 from London. The IFE was pretty much useless for the entire flight. The staff were very apologetic and said that it happened regularly, but usually they could get it back after rebooting a couple of times.
We were given forms which allowed us to choose miles or travel vouchers as compensation, without information about how much of either. One FA thought that it might be $100 or 10k miles, but didn't really know. At a penny a mile, I took the miles

. I do have a bunch of unused miles, so maybe it was a mistake.
So what do you choose when given the option?
Thanks,
Dr. PITUK