I was using M-builds in late 1999 that were reasonably reliable. Many nightlies leading up to 1.0 were usable enough that I was installing them for the computer-clueless that I supported at that time. Just had to find a good one and test it first.
I'm not a fanboy of where Mozilla and its products have evolved, but I see nothing that compels me to change. I would never think of switching to Apple's Mail, for example, refused to use it when I worked for them (which is why I was often the only person that could open attachments). I like that it is simple and doesn't help me too much. The 2.0 builds are working pretty well right now, although the extensions are lagging.
Agree that development and adoption of Firefox took a long time and that IE 6's legacy on the internet resembles W's on the world at large.