I think it makes sense. You're the consumer in the end so even if it is horrible for the game you should have the option.
I think they should make custom soundtracks mandatory but allow developers to stipulate a first playthough without it.
For example, I can understand if ND with Uncharted 2 or QD with Heavy Rain figured that playing for the first time with the Alvin and the Chipmunks soundtrack blaring over everything would ruin the experience. But once you've played through once on the SP (MP being a different kettle of fish) if you want to listen to Gregorian Monks chanting while playing the game then that's your choice.
I think Sony, Trophy's aside, are going for the option right now of giving developers more freedom. While laudable, in truth the results seem to be that few really exploit that freedom while most simply take is as a chance to skip spending a bit of money to support something.
I also want the ability to supress all in-game Trophy announcements as well - something I believe you can do as a custom capability in Heavy Rain.
Try to be reasonable... its easier than you think...
