Did you look at SockJS? It is far more mature than Socket.IO imo. Follows the websocket spec, does not resort to flash for fallback, supports more fallback meth

Did you look at SockJS? It is far more mature than Socket.IO imo. Follows the websocket spec, does not resort to flash for fallback, supports more fallback methods, and later when websockets are fully supported native you just replace "SockJS" with "Websocket" in your code and drop the library.