I don't think Node.js is overrated (where are the ratings, BTW?). I completely agree with @Jan. Use the right tool for the job at hand. But I also have a small story of my own.
When Java was in its infancy (how many of you know that Java 1.0 existed?), we built a "cross-platform" UI intensive tool, and piloted it a large firm. We used AWT for the UI. On our Windows desktops during dev and testing, the thing loaded up in seconds. But at the customer's place, where they used HP Unix workstations, it took minutes.
Of course, they threw us out after the pilot and continued with their antiquated console based tool. The sales guy remonstrated, "We built something that is at the forefront of technology, is it our fault that Java is not what it claims to be?" Those were the times when the phrase "Write once, debug everywhere" became popular, as a parody to "Write once, run anywhere," the byline for Java.
I think Node.js is at a similar stage as Java 1.0 or 1.1. It has promise (I realized the pun later, honestly, unintended), but it also has its place.