If anything, Firefox 2.0 is proof that the browser is now a stable product. The changes from 1.5 are incremental. There is nothing that particularly excites me on the user end.
Of course, to use most of this you’re stuck with Firefox. However, as Firefox evolves further from the functionality offered by IE it becomes more compelling as a platform is its own right. Somebrowser stats show encouraging numbers of people are using Firefox. Give it a few years and IE support may legitimately be optional.