Re in flight mags and using "electronic equipment".
I've flown with BA a few times.... Their in flight mag* (plus web site) says that receivers are fine once the seat belt light is off. I've used my GPS on many flights with subsequent enjoyment when the results have been plotted. Can't always get a signal from a window seat but mostly it's fine. N Atlantic to Denver last month wasn't too hot nor was LHR to LAX last April at times. Brazil to LHR gave a wonderful track all the way overnight (had the GPS between the blind and the window).
Considering most receivers are run from a 1.5 or 3 volt battery, I think they would be hard pressed to generate much interference. LCD screens generate noise (my air band radio will pick it up within about 18" (say 45 cms) of my lap top and personal organiser. Somehow, I don't think that would be strong enough to affect equipment in a modern aircraft.
As for mobiles. They have considerably more radiated power and I reckon it's not a good thing to leave one on. However, I suspect aircraft are more than resilient enough against them.
The "test reports" about RFI and aircraft that I have followed up seem very dated and use language that appears to be deliberately ambiguous.
Lastly, whilst it's no bad thing that all "distractions" are put away during landing and take-off, I think it's a bit "we love telling you what to do" by stating no mobiles are to be on until you are safely inside the terminal. Probably more to do with emptying the aircraft faster for a speedier turn around?
One final thought. In the 1930s, death rays against aircraft were wildly popular. Is there a resurgence?
* I think that easyJet also allow receivers to be used. Will be having a go next month though the route is pretty direct so no surprises there.