Personally I think even though it's an amazing technical accomplishment, the robotic electrode installation might be the simplest part of this whole thing. Once you have the electrodes installed, you might be able to pick out certain patterns, and maybe even restore motor function to people who have lost it.
But the part about being able to replay memories seems incredibly far-fetched. We have no idea how to really interface with the brain. We can only really talk to a small fraction of the neurons, because you can only fit so many electrodes and threads compared to the billions of neurons. It might end up being incredibly challenging to connect a new interface, like if you suddenly grew a tail and had to learn how to control it.