A couple of tools from Nikhil
At my TechEd whiteboard discussion, we talked about a couple of useful things for AJAX development. One is the WebDevHelper that a software architect, Nikhil Kothari, from the team provides. It is an add-in for Internet Explorer that will monitor the inbound and outbound traffic from the browser and log it for you. This can help greatly in seeing what is happening during asynchronous requests. His latest update and post about it are available here: https://www.nikhilk.net/WebDevHelperHTTPTracingUpdates.aspx
We also talked about the problem in AJAX development of the back button. The user can go along interacting with the application while state changes are happening asynchronously. The browser's understanding of the page navigation does not natively correspond to all of those asyncrhonous updates so when the user clicks the browser's Back button, they roll back in the history negating much more than what they anticipated of what they had done. And, they can't recover. Clicking forward again does not restore all of the asynchronous changes that occured after the page was navigated too. Nikhil has a prototype available for makring points in the browser's navigation history. Read more about it here: https://www.nikhilk.net/BackButtonSupport.aspx.