We've made some significant improvements to script debugging!  The VS script debugger hasn't seen real improvements since VS6 (pre-.NET).  Now with ASP.NET AJAX (MS' new AJAX framework), script debugging has caught a new wind.  You can try these out in the new VS Orcas March CTP.

Here are the improvements we've made.  They're all captured on this one screen shot...

Example Source: ScriptDebugExample.zip

1. Set breakpoints in <script> blocks of .aspx files
   You can now set and hit breakpoints on lines inside <script> tags.  The URL in the browser must match the target document file.  Limitations: Redirects, like feeding the default document via a root URL (http://microsoft.com/ instead of http://microsoft.com/default.aspx), will not catch breakpoints.  Also breakpoints in included documents, like master pages or custom controls, do not hit. Some stuff to work on next.
2. New "Script Documents" node in the Solution Explorer
   Many users that script debug didn't even know there was a separate "Script Explorer" tool window that showed the scripts fed to the browser at run time.  We've improved discoverability by removing that tool window and adding a "Script Documents" node to the Solution Explorer at script debug time (with glyphs).  Keep in mind when debugging script, these are the run-time generated script files (the output of the ASP.NET engine), not the original source code.
3. Glyphs & grouping on script object member types
   Object members now have glyphs representing their type.  Methods and Events are also grouped under a parent node.  This helps with navigating the many members of script objects.
4. Text Visualizers on string members
   For string members, we've enabled the three popular managed code debugging visualizers.  Click the magnifying glass glyph to use.  Text = a plain text box, XML renders in IE's XML view, and HTML renders in IE's HTML view.
5. Type data shown for common objects
   Previously, object members just showed up as Object or Variant.  Now they show the actual type, like "DispHTMLSpanElement".  Displaying types is limited to the IE DOM.
6. Debugging Not Enabled notification dialog (not shown)
   By default, script debugging is disabled in IE.  It must be enabled to catch breakpoints or break on errors.  Previously there was no warning that script debugging wouldn't work.  Now, if you attach to IE or run your web project and IE's script debugging is disabled, you get a friendly dialog letting you know and telling you how to enable it.

We Need Your Help: Please get the CTP and give it a try!  Now is the time to file bugs and give us your feedback.  We still have a few weeks to get last minute changes and bugs fixes in.  Your bugs are of the highest priority to us!  Thanks