I converted Patrick to Firebird recently.  Firebird 0.7 came out this week, and I mentioned a peeve of mine was that it reuses its window when launching URLs.  To which Patrick said:>

To always launch Firebird in a new window, put this stuff in your user.js file.

 user_pref("advanced.system.supportDDEExec", false);
user_pref("browser.always_reuse_window", false);

If you haven’t come to enjoy the wicked fast speed and elegant simplicity of Firebird, now is your chance.