Node.js consider to be used in specific scenario. If your app does not fit into that scenario you should not consider it for your app development.
When to use Node.JS
If your server side code requires very less cpu cycle. In other world you are doing non blocking operation and does not have heavy algorithm/Job which consumes lots of CPU cycle.
If you are from Java Script back ground and comfortable in writing Single Threaded code just like client side JS.
When NOT to use Node.JS
Your server request is dependent on heavy CPU consuming algorithm/Job.
Scalability Consideration with Node.JS
Node.JS itself does not utilize all core of underlying system and it is single threaded by default, you have to write logic by your own to utilize multi core processor and make it multi threaded.
Node.JS Alternatives
There are other option to use in place of Node.JS however Vert.x seems to be pretty promising and has lots of additional features like polygot and better scalability considerations.