iPhone 3.0 A2DP bug?

I really liked the iPhone 3.0 update. Just now trying the A2DP profile
and listening over my Bluetooth headset. Everything is nice but wait
how do I control the volume from iPhone. Apparently the only way I can
do is on the headset. Is this a feature or a bug?

Aptera

Got a chance to check it out in Sanfrancisco.