From his website: Rated 4 out of 5 stars

For the moment there will be no update for Firefox 3.0. With Firefox 3.0 the handling of the allowMetaRedirects attribute of the interface nsIDocShell was changed. With this change RefreshBlocker can't allow or deny a META refresh anymore. See Bug 423885 for more details. And please contact me if you know a solution for this problem.

This review is for a previous version of the add-on (0.4).