I think we're fighting a hard battle.....faced with a life-threatening situation and stuck inside a metal tube they have no control over, many pax will simply put things into their own hands, regardless of what the safety video or crew have instructed....
The video below was apparently taken after an Iberia 747 made an emergency landing back at JFK after an engine problem....notice the pax and the opening of overhead lockers to retrieve bags, coats, mascara (you name it). In addition, people seem to be taking their time...granted, there doesn't appear to be a raging inferno, but for an evacuation...
http://www.youtube.com/watch?v=CTcjJoIWJQ4 