Denti, yes, the Bluetooth connection was quite a challenge. Connecting to, yet remaining separate from the IFE system was enough of a headache. The Blutooth connection, as well as Wifi, was a big problem with Apple products (not with Android) as the Apple product is always searching for connections, even when connected. This placed a significant drain on the battery. There is worry that it may attempt to connect to a stronger source while on final approach, hence restriction on use on FA. (especially if the device has been used on the ground with said connection and auto connect is enabled)
It really does take quite a bit of testing and validation before it is even considered to be trained to the crew.
That being said, there are many apps that are taking advantage of the connectivity, especially sharing winds aloft, FMS winds, and FA conditions between the ac in the network. Pretty strong stuff once it gets sorted.