You can't deny Mozilla for wanting to keep user experiences consistent. FireFox 3 is a very solid product and the customize tool bar function lets you put it back to the FF2 style more or less.
Besides, Firefox 3 isn't even bleeding edge anymore. FireFox 3.1 is already on its way and IE8 is in alpha.
besides, here's the FF2 theme for FF3
https://addons.mozilla.org/en-US/firefox/addon/6898