In my opinion it's probably not worth adding unless the highest-confidence suggestion for a particular completion is significantly lower than average. So it informs you when it's especially uncertain and doesn't have anything better to offer, but that's it.

How has tabnine been responding to the development of Copilot? I've looked into it and the most enticing feature to me is the ability to opt out of it using your own code to train (not even sure if that's a correct interpretation)

However it's even more expensive than copilot...