Another philosophical question: what are the quintessential features of Firefox? What are the things about Firefox that remain invariant across different themes, font switches, window styles and other look & feel changes?

1. Tabbed browsing
2. Extensions functionality (most notably Adblock and Gmail Notifier for me)
3. Popup blocking and find-as-you-type

A pretty small list, I would say. This leads me to conclude that the primary reason Firefox has found such large-scale adoption is that it is based on a solidly built inner core (that is independent of the user interface - reminiscent of another such system). At the risk of sounding like I have a fixation on Firefox (which I probably do, considering the number of posts I have dedicated to it), you might even call this inner core the soul of Firefox.

On a side note, I have realised that I hardly make use of the address bar. Most of my browsing is done either from my bookmarks or Bloglines page, or by following interesting links. One use I do regularly put the address bar to is to copy/paste links in my blog posts, of course.

(No, I was not drunk when I made this post)