Back in Ubuntu 11.04, the default Ubuntu themes (Ambiance and Radiance) had the window borders removed. That change was reverted because of some Unity 2D related issues but it looks like borderless Ambiance and Radiance will finally make it into Ubuntu 14.04 Trusty Tahr.

When using Ambiance (the default Ubuntu theme), Nautilus 3 has dark breadcrumbs / toolbar (and menu if you disable appmenu), white background and a gray-ish sidebar, which doesn't look too good if you ask me.

In case you're not using Ambiance, here's a screenshot:

So WarriorIng64 has modified Ambiance to use a dark sidebar for Nautilus 3 and in my opinion, it looks a lot better:

Ambiance Blue is a pack that includes GTK2, GTK3, GNOME Shell and Avant Window Navigator themes, especially designed for those who like the Ambiance theme style but don't like the orange or simply want to try a fresh style while keeping the overall Ambiance look.

Since the pack comes with both GTK2 and GTK3 themes, you can use Ambiance Blue in both GNOME 2 (Ubuntu 11.04 or older) as well as GNOME 3 (Ubuntu 11.10) - or other Linux distributions, but for the GTK3 theme you'll need to install Unico GTK3 engine.

Ambiance, the default Ubuntu theme, will get a dark toolbar very soon. The news comes from Andrea Cimitan who has posted a screenshot on Google+:

(The theme is not yet available in Oneiric)

A new Bodhi Linux 1.1.0 was released yesterday bringing an updated Enlightenment SVN Build (as of May 05/23/11), Linux Kernel 2.6.39, Intel 2.15 drivers, Midori 0.3.6 as well as some repository updates such a Nvidia 270.41 driver, Chromium 11 and Firefox 4.0.1.

Other changes in Bodhi Linux 1.1.0 include a new boot splash and LXDM as well as 5 new themes you can choose from: Ambient, Boox, Elegant, LG2, Moonlight.