BC is convenient for the first couple months when the new console is out, after that I never touch it again.
Come to think of it, BC is probably bad for sales of the current systems. Many people will be selling their old systems since they can play all the games on the new system. I never sell my old hardware. It's always nice to boot up the ps3 again and 'find' all the stuff I collected on there.
BC only gets more relevant since there is nothing much to be excited about for launch games :/