Since the hide menubar function has been integrated into Firefox 3.6, all you need for the good looks is the All-Glass add-on. It also renders your tabs fully transparent - that's how I prefer it. To sum it all up:
- All-Glass for the Aero effect
- Kempelton for great looking icons
- Scroll Zoom Button (because I'm to lazy to hit Ctrl+0 while browsing)
- to hide the menubar > right-click and deactivate it. Press Alt to make it visible
Some of you might be interested in the Firfox 4 Mockup Theme. Allthough it looks good, to me it's still "to alpha" ...