Sadly the parser is fairly synchronous. I would be nice if they took the SAX-ish approach of firing events (which I guess you can on top of this). Then again, I suppose there are already a couple of SAX JS implementations.
Someday, someone will implement the W3C DOM API in node so that it's possible to parse XML with the same code on both the client and server. Until then, I guess I'll keep serving with xpcshell.
jsdom is great if you want to parse HTML and don't care about speed. The last time I tried it (which was <1 year ago), jsdom didn't have full support for namespaces, so it's not so great if you want to parse non-trivial XML. I haven't tried dom.js, but until recently, I don't think it would run under node at all because it needs proxies and WeakMaps.
Even for HTML, jsdom is too slow to use in production, at least for our use cases. (My tests run at least one order of magnitude faster in xpcshell. I can easily download HTML faster than jsdom can parse it.)
