Netscape 6.1, the new browser based on Mozilla is fully skinnable, and in its latest version very fast and stable.
Check out the newest version under www.mozilla.org, and check out the cool default skins. Then go to View - Apply Theme - Get new Themes (http://x.themes.org/viewresources.phtml?type=chrome) and check out the cool themes already available.
Now comes the important part: WinCustomize needs a N6 / Mozilla themes section & some theme skinners. Any takers?