I’ve been having Bluetooth audio lag issue since very early release of OS X Yosemite Developer Preview.
It only happens in closed clamshell mode. I connect my MacBook Air to an external display on a daily basis and close the lid most of the time. Audio output to a Bose SoundLink Mini speaker or Sony ZX750BN headphone. For both devices, I notice the audio lag every 1 or 2 seconds.
This totally kills my pleasure of listening to music, podcasts or Internet radios.
Many users are complaining about the same issue. I’m not sure if they have this problem when their lids are open. For me, if I open the lid, then Bluetooth audio is fine.
Before Apple releases an update to fix this, my solution is keeping the lid open when connecting to external display(s).
Update Nov 4, 2014: 10.10.1 seed seems to have improved (if not fixed) the Bluetooth audio. Listened to music for more than 1 hour without any lag today. Yet to see if this is persistent though.