Once Firefox supports SSE I agree that it would be easier to implement in many use cases. Although it doesn't have the same sort of fallback mechanisms available to it that WebSockets have (ActionScript sockets).
Here is some additional information about it that I found at stackoverflow: http://stackoverflow.com/questions/5195452/websockets-vs-ser...
You can fall back to XHR with long polling — the stream is trivial to parse.
• it's pure HTTP, message format is dead simple ("data: payload\n\n")
• browser handles network failures and reconnections automatically.
• browsers can share same stream URL between windows
His use-cases with to-do app and analytics were good fits for SSE.