The truth part is that these devices will last so many hours. And by using USB 1.1 you burn up some number of hours on the hardware.
However, since you may play the unit for hours at a time, the heat item is going to be the urban legend item.
I have just bought a new ipod mini and am very impressed....my laptop however only has one usb 1.1 port and it runs quite slow......i have heard somewhere that running the ipod on usb 1.1 can cause damage to the unit de to excessive heat etc....is this true? if so how do i combat this problem? i dont really know how to open up my laptop to put a usb 2.0 card in, that is if it is possible.