Waiting for seatbelt sign can be bad, if the captain is forgetful, or if it's just turbulant. I've been over Russia (Kalingrad) in the past before the sign has gone off.
I take the cabin crew out of seats as a sign that IFE can come out and electronics can go on. I suppose 10,000' would be another point, but there's no indication when that is.
And despite seeing a variation of a BA safety video 2-3 times a week (In the last 7 days, an A319, A320, A321 and 773 version), I always watch and listen, from the first words to the "as we prepare for takeoff" bit.
It's a shame the cabin crew on my recent FCO-LHR flight couldn't be bothered pointing out the emergency exits -- she was too busy laughing at something the person behind her said.
I have idly wondered if
"engines are running on the ground, during takeoff, approach and landing"
means that electronics can be used if the engines aren't running during approach
