While lazily browsing the web (instead of working :-) I stumbled upon Jesse Guardiani's site, who put together a bluetooth a2dp hack. I found no reference about it on the forums so I'm reporting it for others to try. I myself have no bt headset, but if it proves to work I might get one :-)

Here's the page: http://www.guardiani.us/index.php/N800_custom_packages#Bluetooth_ALSA

Have fun...