Requires no basic knowledge of nodejs or socket.io, simple and easy to learn

The best thing I like socket.io is its latency. For messaging between two nodes it fulfill the purpose quite performantly and easily scalable.

For an appplication I am building, Socket.IO has greatly simplified passing of data between a server and many clients. Documentation is good but takes a bit of time to read through and figure out how to get started. Once you have the socket connection bit working though, adding new socket.on() functions for client-server communication is very straightforward. Socket.IO is a great alternative to other client-server communication methods such as REST.