Does minifying impact performance of Node.js?
Yes, it improves compile-time performance, but compile-time is so insignificant to the overall lifetime of your process that it shouldn't matter. The only difference would be if you're constantly starting and stopping node programs for some weird reason, which if you're doing, is probably wrong.
You won't want to uglify your server-side code, however, because if you get an error back, you'll want to know where in your human-readable code it is to find it and fix it.
I bet the real question is: Do you think the almost insignificant compile-time performance will offset the time it saves to debug your code instead?
The answer to that would be no, just stick with normal human-readable Javascript instead.