Script Debugger: IE8 Beta1 comes with Script debugger and IE8 team made it even better in IE8 Beta2. IE8 Beta2 Script debugger include let’s you to see the code in syntax colored manner that you see in most of the code editors. Console show all errors at one place and developers can use "console.log" feature to log errors. IE8 Beta2 console is extensible, means developers can add their own commands through custom scripts.
Script Profiler: Script Profiler is a new feature in IE8 Beta2. Script Profiler help developers to find and fix performance bottlenecks, resulting in a better Script that will be efficient and run faster on browsers. The Script Profiler comes with an easy-to-use UI and powerful features such as ‘Call Tree View’ and ‘Export’ functionality. The Profiler output can be exported to tools like Excel so you can visualize the execution times through charts and graphs.
What’s New for JScript in IE8? Video