It's probably fair to say that the aircraft isn't going to crash, but that doesn't mean that unauthorised use of electronic equipment isn't going to cause any problems. What get's on my nerves are those passengers who decide that they know better than the crew and think they are exempt from following the crew's lawful instructions.
I've experienced interference from electronic devices in various different classes of aircraft that has had effects ranging from severe difficulties with navigation and communications to simple distraction. If passengers are told to switch off their toys there is a damn good reason for it.
The last thing I want when approaching minima on an approach at night in crappy weather, tired on my fourth flight of the day and needing clear comms and no distraction, is to hear the buzz-buzz-b-b-buzz of a GSM phone trying to get a signal because someone can't wait a few minutes until we've arrived and shut down. If the individual stopped to think about it, he probably wouldn't want that either.