We've basically known how Firefox 3.7/4.0 will look like since... forever, but up until now you had to install a custom theme to get that look.
The latest Firefox 3.7 nightly builds finally add some of those theme elements, but for Windows only. And no Aero, tabs on top and all that, just the buttons (icons):
Hopefully Linux users will get the new design in Firefox 3.7 nightly builds soon.
You can download the latest Firefox 3.7 nightly build from HERE | via downloadsquad
You can download the latest Firefox 3.7 nightly build from HERE | via downloadsquad