According to the recent article on an extra robotic thumb, people got used to it very quickly. And that one wasn't even controlled by neural link, but by sensors on the user's toes.

https://news.ycombinator.com/item?id=27218940

We adapt to controlling countless complex things; I'd imagine we'd adapt very quickly to controlling these.

I'm not so sure. We're good at controlling things with lesser degrees of freedom than our bodies naturally possess. I am not sure wed be very good at controlling things with more dof unless it was very high level octopus arm type control (arm, get the red ball and drop it here)

FPV drones are good counter-example to this.

A quadcopter has 6 degrees of freedom. A single human arm has 30 degrees of freedom.

I'm sure people will adapt, but probably not very quickly.

Of course, it depends on the level of proficiency you want to reach. But it's already hard enough for people to eg learn to play Tennis, or learn to play Tennis with their left hand, when they normally use they right hand.

I think so too.

i believe it would be quite difficult. if you actually look at the structure of the human brain (eg the homonculus model of the cortex) you will note that a very large portion of the brain is dedicated to just the hands/manual dexterity. Many of the current neural prosthetics seem to act by attempting to leverage the brain's use of already-existing neural pathways being used for other functions. Sort of a "turn on my microwave when i open my refrigerator"-type dependence. I think a good sign of truly independent supernumerary prosthetics would be if some users reported phantom limb sensations in their absence

Lots of humans adapt to fine control of cars relatively quickly, and that's through the clumsy mechanisms of steering wheel, pedals, and shifter.

The human ability to adapt and incorporate tools, objects and use them naturally to perform complex tasks is so impressive and interesting.

Driving, cars, flying airplanes (including sitting 10m+ off the ground in cockpit in a 747). Things like playing ice hockey, kite surfing etc. Highly complex activities (including interacting with several others and even plan ahead), often performed at speeds way beyond what a human can move about.