Same thing. There are a few aesthetic changes but other than that its about the same. One thing I noticed was the tabs you can directly click on them in order to get rid of it other than that nothing mind-blowing.
actually i like firefox 2 a lot better than firefox 1...maybe i was slow in updating but my impression with firefox 1 was that you couldn't change the order of the tabs...with firefox 2 you can drag the tabs around once the windows are already open, so you can cluster relevant tabs together even after they've been open