I'm using Ajax View [1] more and more and find it very useful.
The goal of the Ajax View project is to improve developer's visibility into and control over their web applications' behaviors on end-user's desktops.
The Ajax View approach is to insert a server-side proxy (or web server plugin) in-between the web server machines and the end-user's browser. This proxy captures the web application's JavaScript code as it is being sent to a browser and rewrites the code to insert extra instrumentation code. The injected instrumentation code runs with the rest of the web application inside the end-user's browser and can capture performance, call graph, application state and user interaction information, providing visibility directly into the last hop of the user's experience.
Download the first release of the client-side prototype [2] which requires Windows Vista, Windows 2003 or Windows XP SP2. Read the short documentation, showing a simple walkthrough Ajax View's performance profiling [3].
Well, there are some known problems using this tool. Sometimes https requests block everything, or JavaScript files could parsed correct, but if you have only one Web browser with the URL to test opened you are ok. I hope they go on with the development of this tool. If you find bugs please report them to the project members [4].