I've just done it. I'm not exactly familiar with the idioms and I'm sure there are constructs I've not yet encountered, but it's to be expected that broad knowledge will take time.
Of course I had encountered JS before, around HTML/browser, but had never tried doing any proper coding with it. It certainly doesn't lack power, but one drawback I'd say is that its flexibility means that it isn't always obvious what's going on. That goes double for node.js, where having callbacks everywhere can make things confusing (though I'm beginning to get used to that).
The little app I've put together is much more concise than it would be in the languages with which I'm familiar (mostly Java and Python), but then needing a lot of comments to explain what's going on isn't a good smell.
However, if my vague understanding of how node.js works is remotely correct, I get performance/scalability for free (something that'd need a lot of thought in Java/Python). node.js really does lend itself to Web wiring.