I found Node.js to be quite difficult to work with, mostly due to nature of Javascript. Module ecosystem is vast, but each one has an API written in a different style. Combine that with no type-checking and lack of robust IDE auto-completion (Webstorm is quite disappointing at the moment) - and you get a frustrating experience. Oh, and also add asynchronicity into the mix.

Making restful APIs is quite fun with it, though.