Its not April fools sh!t. Look at Mozillas addons page, when you don't believe this.
Noia FF4 Hack v4
Noia2v3.76 FF4 Hack v4
- tabs have now correct backgrounds and sizes (ff4 default)
- ff4 button is now transparent
- url dropmarker fixed
- go/stop/reload button fixed (again)
- urlbar improved
- added more cutemenu icons (from Nuvola)
- some more fixes/changes/improvements
Noia2v3.76 FF4 Hack v3
- fixed tabs on top
- fixed FF button & menu
- a lot of oher fixes
Noia2v3.76 FF4 Hack v2
- FF4-button menu doesn't work properly, switch to menubar
- extensions menu button fixes
- go/stop/reload button fixed
- Noia options removed (didn't work on FF4)
Noia2v3.76 FF4 Hack v1
- first release (was not really usable)
- installs on FF4
Still some small glitches left here and there:
- buttons in the popup after addon-installation
- button in toolbar customizing menu
I think you can live with them
Many fixed are directly from Nuvola theme.
Runs fine on Windows 7/Vista with Aero and on WinXP. OSX maybe won't work properly.
Runs on Linux (onfirmed by sgrayban).