I have fixed bunch of reported bugs (thanks to all who took the time to do these reports!) and solved some compatibility issues with Firebug 1.4. See release notes for more details.
There is also a couple of new enhancements. In case when the cookie value is JSON or XML, there are additional tabs in the UI that present the value in more readable format.
If the value is formatted as JSON, there is a new JSON tab (selected by default) displaying the value using expandable tree. Similarly as for network responses in Firebug's Net panel.
If the value is valid XML document, there is a XML tab (also selected by default) displaying pretty printed & colorized XML (I think there could be something similar in the Net panel for network responses).