I was recently given a Jabra5020 Bluetooth headset (thanks David!).
It took quite a bit of work to get it to work, allthough in the end the solution is rather simple.

1. install the appropriate Bluez and Alsa packages (sudo aptitude install bluez-audio bluetooth-alsa on Debian).

2. Add

pcm.bluetooth { type bluetooth }

to /etc/asounc.conf OR ~/.asoundrc

3. Put the headset in connect mode (by holding the "on" button for a few seconds until the light becomes blue).

4. Direct audio to the alsa blueooth device, for example: mplayer -ao alsa:device=bluetooth *mpg

5. Enter 0000 in the popup that asks for a pin-code.

The tricky thing is that the headset only works once, and then the driver has to be restarted. ("modprobe -r sco; modprobe sco"). That's a bit annoying, but not unacceptable, as I don't see myelf using it all that often. As long as it works on the first try I'm farily happy with it.

Unfortunately the sound quality is rather poor. I have no idea how it compares to other bluetooth headsets, but it was far worse than any wired headphones.

There is an alternative protocol around called A2DP that is supposed to deliver superior quality, but I was unable to get it to work. I'm not even sure of the Jabra 5020 supports this protocol at all.