And are looking to centralize them in a way that allows for: Github authentication, search / indexing, internal commenting / discussion.
It provides ability to create documents with markdown text, images, executable code and output all within single document. Although it's optimized for infrastructure runbooks, it can be used for any internal documentation. Reports, metrics, onboarding guides, design documents etc.
If you don't foresee any need for executable code then it's probably not for you. I have seen teams use Dropbox paper, Media wiki, and sometimes Gdocs for static internal documentation.
Nurtch's primary use case is quick incident response for any operational issues. E.g. service outage, dependency failures, database acting up and such. Rubix library (bundled with Nurtch) helps with diagnosing and acting on these issues.