I am a frequent WebSocket user. WebSocket is perhaps the single-best thing that has happened to web development since the introduction of HTML5, due to its bi-directional and ‘real-time’ characteristics.
I have frequently used a websocket conncetion to keep the client up to date with regards to changes from the server, especially when doing game related development.
The transport channel is simply a websocket connection, thus anywhere websockets are supported SignalR should in theory be supported. In addition, SignalR is 100% open - allowing anyone the possibility to implement a SignalR client or server for any other language.
I have yet to tryout the library myself - but it is definitely on my to do list!