[pfooti]

Socket.io also transparently handles sessioning and resuming of sessions (automatic reconnect), namespaces, filters, and a ton of other useful stuff for a moderately-complex application. If I'm just sending events between client and server (say, live-updating a common twitstream), regular ws is fine. But if I'm selecting and reflecting certain events to other connected clients by room, and don't want to worry about stuff like "oh hey, that guy needs to re-handshake because he lost network", socket.io provides a lot of useful sugar.