Bluetooth audio codecs still leave a lot to be desired, and are pretty far from the cutting edge of compression to put it mildly. You can get good audio, but you have to be very careful with your combination of headphones and output device, because a lot of combinations don't have the same codecs, and you end up with the lowest common multiple. There are new standards in development, though, so I think this will be largely solved in about 5 years.