2.0 is out, too.
"Note: Firefox 1.5.0.x will be maintained with security and stability updates until April 24, 2007. All users are strongly encouraged to upgrade to Firefox 2."
http://www.mozilla.com/en-US/firefox/
I'm sure there will be bugs with the new release so I'm waiting for the first security/bugfix update on 2.0 before downloading.