Volume keys are equally hard to push. And if the N900 is playing music then it's not really asleep. Most music phones/mp3 players work just like that, they allow you to use the hardware keys to change volume/skip tracks/etc even if the device is locked. Since it doesn't sound that much of a technical difficulty, you would expect the N900 to be capable of that.

But I guess "power button -> what actually matters" isn't that bad. Here's hoping 1.2 comes soon.