Huh? Pairing worked like 10 years ago. And sending files between phones. Everyone in school was sending J2ME games/apps around :D Audio with media control also worked. And modem (using the phone's GPRS/EDGE connection on a PC).
for audio, right?
But when iOS/Android smartphones came on the scene it took a huge step back in reliability. A2DP also took a huge step back in audio quality until the new platforms tweaked their SBC parameters and added in MP3/AAC support.
The craziest setup i ran with back then was a Nokia N800 paired up with a Sony Ericsson C702 and a no-name folding keyboard. The C702 was also paired up with a pair of Jabra headphones/headset.
At certain times all of those could be in use. The C702 acting as the modem/router for the N800, whole also playing music through the Jabras, and me typing comments on the Maemo forum etc.
The only times there were a hitch were when i used the modem profile between the N800 and the C702, rather than the PAN. Something about the intensity of chatter or something between the two made the music and keyboard stutter.
Do note though that headphones can act up if you are out and about with little for the signal to bounce off. Best then to have all devices on the same side of the body for less obstructions.