iPhone 3.0 is bringing stereo bluetooth to the 3G and 3Gs. As for the ops question, I've read different things online. I would tend to think that once your headset is paired, it would work just like if you have a normal headset plugged in (ie, all audio would be routed through it). However, I read somewhere (and I can't find it now, of course) that apps would need to be updated to allow you to select which output to use. That could mean that apps only need to be updated if they want to allow you to use an output that's not the default. If someone with the 3.0 software could try this out, that would be awesome!