Actual stereo sound with bluetooth headset
Are you still having this issue? I found this set of changes fixes the output, though I'm still having tinny input quality over bluetooth:

defaults write com.apple.BluetoothAudioAgent "Apple Bitpool Max (editable)" 120
defaults write com.apple.BluetoothAudioAgent "Apple Bitpool Min (editable)" 80
defaults write com.apple.BluetoothAudioAgent "Apple Initial Bitpool (editable)" 120
defaults write com.apple.BluetoothAudioAgent "Apple Initial Bitpool Min (editable)" 80
defaults write com.apple.BluetoothAudioAgent "Negotiated Bitpool" 100
defaults write com.apple.BluetoothAudioAgent "Negotiated Bitpool Max" 120
defaults write com.apple.BluetoothAudioAgent "Negotiated Bitpool Min" 80
defaults write com.apple.BluetoothAudioAgent "Stream - Flush Ring on Packet Drop (editable)" 30
defaults write com.apple.BluetoothAudioAgent "Stream - Max Outstanding Packets (editable)" 15
defaults write com.apple.BluetoothAudioAgent "Stream Resume Delay" 0.75