UPDATE: Yes, as of the release of iPhone OS 3.0, the iPhone now supports A2DP.
Many of today's newer wireless devices (i.e. the Samsung Blackjack) support A2DP audio output. A2DP audio devices, such as stereo bluetooth headsets, offer high quality listening ability without those nagging wires. As the iPhone is birthed from the iPod, and is undoubtedly the most music oriented phone ever to be developed, surely the iPhone supports A2DP, right?