Hi,
I started using a BTD400 on a 2011 MBP running OS X 10.9.5 because the internal BT adapter becomes unresponsive too often after a wake-from-sleep.
The first time I tested the new dongle (when the internal adapter was unresponsive) it worked immediately but pulling it out (without turning off BT first) cased the internal trackpad and both the internal and external keyboards to become unresponsive. I had to connect over VNC to close my session and reboot properly.
Yesterday I tried it again after rebooting with the new nvram parameter set and the BTD400 connected. The internal adapter was being used (AFAICT) so this time I did turn off BT before yanking the dongle.
Is there a best practise to remove the dongle? I hope this is an officially supported “feature” because I’ll have to remove it when I take the laptop elsewhere!