Well, Zumo BT has its problems. Dunno if its repaired by a new firmware but I had problem with my carlo device and simply let Garmin unconnected.
Like the idea of having the phonebook in Garmin display but listen to the navigation voice ordering me to turn all the time.
Also the GPS is ahead of every other connected, so if you are chatting with your friend, it is telling you to turn and break the conversation.