I run a production node.js app and my experience hasn't been bad. My cofounder and I spent more time in the beginning (not much more time, mind you) learning how to deal with multiple outstanding async calls, a good application structure for express, etc. Now it's just as fast for us to go in and add a new API call that does this one query in node as it would be in another system.
The only technical problem I've seen that node is an easier solution is dealing with third party apis concurrently. It wouldn't be very straightforward to have a redis query, a mongo query, a facebook query, and a sendgrid query all open at the same time and managing the results when they all come in (and keeping program flow maintainable) in PHP, Python, Ruby, etc. Probably not a common problem or desired feature, though.
We're 100% Node on heroku with a custom buildpack, using a hosted Mongo service, some Node written cron jobs (which were pretty interesting to write), and redis and we serve 5 digits worth of hits every day at least, and I'm more than happy with performance. I never once look back and regret the decision to use node. I don't necessarily care about sharing code, having frontend developers do everything, etc like some node guys throw around naively, but I am looking forward to bringing somebody on that can grasp adding in a new API route, throw in a Mongoose find, and render a template with some variables. We have EJS templates serverside and clientside for that reason, and that could just as easily be done in PHP or Python.
However, I am enjoying working with node, the node community, and the interesting modules and stuff that are being released. I will say that there's a good bit more active "lets hack this up into a module and open source it over the weekend" kind of people in node than others at the moment.