PDA's on board
 

Having recently acquired from my employer a PDA (Palm Vx = Expensive Filofax), do airlines (particularly Big Airways) regard them in the same category as Laptops for use in the cabin ?

Pretty much all airlines have the same general rules regarding electronic gear. They do not generally differentiate between PDA's or laptops.
No Radio Frequency transmitters are allowed (mobiles, radio controlled toys etc.)
Some airlines I have flown specifically forbid the use of peripherals attached to laptops (such as printers). At least one European carrier forbids (or used to), all digital devices, which includes PDA's and personal CD players - strangely, they allowed personal tape players with potentially electrically noisy DC motors.