As documented at http://blog.nodejs.org/2013/03/11/node-v0-10-0-stable/ and http://blog.nodejs.org/2012/12/20/streams2/ the new stable version of node changes the streams API. As noted there, "Old programs will almost always work without modification, but streams start out in a paused state, and need to be read from to be consumed. WARNING: If you never add a 'data' event handler, or call resume(), then it'll sit in a paused state forever and never emit 'end'."
That matches the behavior I saw when I tested parsoid with a node 0.9 prerelease -- node api/server.js appeared to "hang" without ever doing anything. I didn't do any digging to find out which part was failing; it could well be one of our npm dependencies which needs to be updated.
As discussed in bug 45993, it appears that a monkey-patch we're doing to domino also stops working in node 0.10. I'm hoping we get an new upstream release of domino to fix that.
There may be other issues with node 0.10...