I'm a JavaScript and Lisp (Clojure) programmer, so I may give you an unbiased answer.
Node.js is great because is Js, and that means:
great community
huge ecosystem (someone already wrote an npm module with the functions that you need)
quite easy to learn
reusable skill all across the stack
JavaScript is a great language (despite all the WTF)
The bigger drawback is that Js was created to run in a brower, so if you need to use it in another environment, you basically need to embed the all "browser ecosystem"; and that could mean bad performances.
My advice is to learn pros and cons of every instrument you can use and choose the best fit for every project.