[b5n]

I just use whatever is in debian testing or unstable, but it's trivial to download firefox _directly_ from mozilla which will then keep itself updated to the latest version.

This just chucks firefox in /usr/local but its straightforward to edit and use ~/, opt, etc., just make sure the created symlink is somewhere in $PATH. Desktop integration will depend on your DE/WM, but should be pretty simple to figure out if not automatic.

    wget -O firefox-latest.tar.bz2 \
      "https://download.mozilla.org/?product=firefox-latest-ssl&os=linux64&lang=en-US"
    tar xjf firefox-latest.tar.bz2
    sudo rm -rf firefox-latest.tar.bz2 /usr/local/bin/firefox /usr/local/firefox
    sudo mv firefox/ /usr/local/
    sudo ln -s /usr/local/firefox/firefox /usr/local/bin/firefox

[blackle]

This is what I do with Firefox developer edition. It doesn't have that problem where it refuses to work if it's been updated in the background, it just adds a little green dot to the hamburger menu that indicates that it wants to restart at your leisure.