Deeper and deeper I dive into HTML 5. The WebSocket API allows bidirectional communications with a server. Think of this one as how you wish AJAX would have been. Not only do you have Server-Sent Events with HTML 5, you can actually have multi-directional communication with any web server.
This really opens up the possibilities of making web applications more real-time.
You can make your HTML 5 web application communicate, collaborate and receive updates in real-time through web sockets and server-sent events. Definitely a big step in the evolution of web applications.