I've had to teach somebody NodeJS so that they could take on a JS-dev job, so had to learn NodeJS in a day, transfer all my knowledge to that person who also never used it before and haven't used NodeJS since.
At least that person got the job and is now a NodeJS + AngularJS developer, so I'll learn from them again :-)
NodeJS is interesting, I might use it in the future when I start a new project, but for now I've got too much code in Java which would go to waste if I make such a switch on an existing project.