We've seen mockups on how Nautilus 3.0 should look like, but I for one have never seen a screenshot until now. Well, Cosimo posted a screenshot of the new Nautilus 3.0 - currently in beta:

As you can see, the Gnome devs have done a great job turning those mockups into actual code. In the above screenshot you'll notice a new sidebar design, a floating statusbar and a streamlined toolbar.