Just want to add to the discussion.
I've also experienced problems with BT audio since I upgraded to Yosemite (10.10). Sometimes it seems as if audio is 'repeated' partly, which means that get something like thi-this, and i-it's REALLY annoying! I'm not sure if there is a an actual lag in the audio.
Initially I thought it might be related to my audio device (Jawbone Jambox), but now I'm also experiencing the same problems with a BT headphone (Philips SHB4000). It's also not really related to specific Mac hardware, as I'm experiencing the problems with both my macBook Air (13" Mid 2013) and an older iMac (21" Spring 2010).
The upgrade to Yosemite 10.10.1 didn't bring any improvements, and now I'm hoping that the 1010.2 update will solve this issue.
Finally, a more technical remark on the issue: So currently I'm experiencing this 'doubling' (don't know how to call it otherwise) of short parts of audio, but I don't experience a real lag. Also not something like an increase in lag after some time. This brings me to believe that there's a problem with the communication stack itself in the way that audio packets may be lost, and then retransmitted, and re-amplified; or something like that.
It can't be that the macBook's transfer rate has increased, so it is (a little bit) higher than the audio device's receiving rate? Maybe stupid thought, but might be worthwhile to check...