Want to build a realtime analytics platform? Node has you covered. Want to build a super lean and powerful server for an iPhone game? Node also has you covered. Want to build a web application that doesn't require anything realtime? Not so much.
Node serves a purpose for a lot of things, anything that requires a lot of connections and continuous streams of data it is a perfect fit, but nothing much else.
As for the Python remarks and websockets, I find Beaconpush does the job well: http://beaconpush.com/ - the server that drives Battlelog on Electronic Art's game Battlefield 3 is a python framework with websocket support, I believe it uses Beaconpush.