The new version is still in Beta, but should have more functionality than the older version of Firebug - it actually seems more stable, as on some sites the old version of Firebug would crash my browser.

If you have Firebug on Firefox 2.x, Firebug does not automatically upgrade. You would need to uninstall the old version and manually upgrade to 1.2.

__________________
The best way to learn anything, is to question everything.