Well first of all it's always a good idea to learn different languages and frameworks. A common point is that learning for instance ruby makes you a better X developer.
I'm using Node.js since almost 2 years now besides other technologies like PHP and Ruby. During those 2 years my javascript knowledge and understanding grew a ton compared to just "playing" with jQuery, Backbone etc. Also my understanding for asynchronous code (both javascript and non-javascript) increased a lot.
If you don't care about Node.js or don't like javascript (on the server), try Ruby or Python or Scala or whatever. There are so many different and awesome things out there, especially for building web applications. It would be a shame to work with PHP/MySQL all the time.
What really kept me in developing Node.js after the first few weeks was the amazing community. Basically everything is Open Source and happens on Github. New development happens basically on a daily basis, really impressive. And there a tons of awesome modules out there, from template engines to testing libraries.
So bottom line: I don't need to convince you to try Node.js, but I do want to convince you to try something else (not just in terms of languages and libraries - try different databases like Postgresql, MongoDB, CouchDB etc. as well. Working with MongoDB for more than a year also taught me a lot).
Btw: "Scaling" and "performance" doesn't really cut it, since Node.js isn't necessarily faster than other tools, it always depends on the type of application and the developers/admins knowledge.