What's the usefulness of this method? What does it enable researchers to do that they couldn't before?

Vitrification turns brain tissue preservation from a purely structural possibility to a functional possibility.

So the immediate research implication of preserving viable tissue is that experiments aren't restricted by time or location.

This improves reproducibility, could reduce animal use and make many areas of the human neocortex available for electrophysiological and other types of experimentation for the first time.

So it could advance basic neuroscience, also neuropharmacological drug testing.

and also other types of research that heavily depend on realistic human brain tissue that has been exposed to environmental factors and matured within the skull for decades.

This is something that you cannot easily model in a tissue if you compare it, for instance, to a cancer cell line.

vitrification could