What a disaster!
If your happy with the 1.5 version, stay with it. I upgraded to 2.0 and man was I sorry I did that.
Tons of problems with favorites and trying to get preferences set. There is an entire page donated just to solving one bookmark problem. Another 2 pages trying fix the "save preferences" button.
I like firefox, but 2.0 was released before it should have been. For some users, there are major problems with important features.