Just downloaded WebStorm and giving Node.js a try.
Unfortunately the autocomplete does not seem to work.
I have set the node js interpreter to node.exe but saw a post saying that I should set it to the Node.js file. When I used Node.exe, at least the version was populated in the Node.js configuration dialog, however when I download the code and select the Node.js file I get "Version not found".
Either way, autocomplete does not work.
After doing a "Invalidate cache" all appeared to work.