A Firefox developer has posted a handful of mockups of Firefox 4's user interface redesign along with some explanations of this shiny new App Button we're getting. Everything just looks oh-so-gorgeous and simplified right next to that old 3.5 design.

The main focus of this new design is the App Button, a space-saving touch which will feel familiar to Windows 7 users. In essence, it "provides a unified location for menu items" and cuts down on all the toolbar clutter.

You can check out Horlander's site for plenty of details about the design and explanations behind some of the new elements, but before you go, tell me: Do you prefer this App Button sort of element? Or do you prefer the plain ol' menus we're used to? [Stephen Horlander via Neowin]