Have you tried Haskell? Why haven't you tried Erlang? They're both good choices for writing applications that handle making and receiving thousands of concurrents requests because they have very fast lightweight threads and good exception handling and you don't need to write the kind of code that Node.js forces you to write.
Node is appealing because Javascript is ubiquitous, but I doubt it's harder to learn Erlang than it is to learn to write everything in nested callbacks.
That's why I mentioned that I hadn't tried Erlang. It was one of my first choices, but the library support wasn't there. Tolerant HTML parsing is a requirement for the project, and there doesn't seem to be any good parsers for Erlang.
