There’s two pieces of data that’s critical for several apps to get from Firefox: the current URL and the current Title. The title portion is broken in Firefox 3. That’s a regression from Firefox 2. Except, it isn’t officially, since Firefox never officially supported AppleScript. There were just some good programmers who added it in.
So what happens when you request the title? It returns random garbage data.
I’ve also gotten reports of intermittent problems getting the URL via AppleScript.