Connection breaks regularly (less often with more expensive headphones). Even when using an expensive Creative Bluetooth audio dongle. Samsung Android phone built-in breaks less often but in many cases the whole BlueTooth stack crashes.

Untolerable sound distortions start occuring every now and then. Even under Windows on a new EliteBook with reasonably expensive earphones. Often also with the smartphone when I jog in the woods (tried with different headphones and earphones).

With a cheap full-featured dongle I use on the office PC the sound quality is often untolerable (I mean distortions, not the bitrate, some days it would work Ok whole day, some days it just doesn't).

Built in BlueTooth in my old Dell Latitude only worked with Windows and occasionally with Ubuntu, other distros thought the device was a trackpad (could be fixed with some hacling but was not worth it because still worked unreliably so I used the Creative dongle instead).

Even with Apple (but non-apple headphones of the middle price segment) the connection breaks occasionally although not very often.