>>16
Mozilla <= 4 and Mozilla >= 0.6 (how counter-intuitive) are different codebases maintained by different people. I said "Mozilla 1.x" in reference to the latter.
Back in the day, they were much more interested in improving and promoting Gecko than the UI, so I don't find it surprising that they had a lot of false starts before revamping the UI with Firefox.
Firefox's simplified UI was a problem for me, too. I'd seen enough slow, buggy and ugly Web sites to develop an impression that plug-ins == bad, so I held off installing Firefox extensions for a long time (under the mistaken assumption that extensions were as dysfunctional as plug-ins).
Mozilla's inclusion of heaps of features into the base distribution at least ensured that everyone saw that it was capable of more than the bare essentials offered by IE.