When Windows developed IE 9 they were extremely proud, because it was downloaded 2 million times
on the first day of its release.
Well, Firefox 4 did a little better.
It was downloaded 6 million times within the first 24 hours and
it has reached 23.5 million downloads so far [March 25 11:40 GMT]!

Just visit the glow Mozilla site and see how many people are downloading Firefox 4, right now.

Its secrets?
It's free, it runs on practically every operating system and it doesn't need to waste millions on advertisements.
Mozilla seems to spend most of its budget on improving its products.
Word of mouth [social network] is enough when you have so many satisfied users.

Fast, simple, hundreds of adds-on, secure.
It is open-source, which means that hundreds of hackers contribute to its source code every day,
so  it's constantly being improved and debugged.
They're the volunteer superheroes all around the world that help us out when something goes wrong.

For a quick survey of how to use the new tools of this awesome browser,
check out the summary
HOW TO: Start Working On Firefox 4

The more curious and  tech-savvy will probably read the
Firefox 4 Beta Reviewer's Guide - Mozilla [PDF]
and of course
Need Help With Firefox?
with tons of information about every aspect of this cunning fox.

Personal opinion? Don't miss it, guys.
Because it is really amazing and
it'll certainly be getting even better!