simple adaptation of the elegant brit gtk2 theme to gtk3, still missing a few things, like exceptions for programs like unity and nautilus, but otherwise it works pretty well considering writing gtk3 themes with no central documentation is hell and a half.
requires the adwaita engine
the zip includes the theme folder, which will work if you just extract it into /home/user/.themes/
how to get the original elegant brit: [link]
UPDATE (July 16th 2012): cleaned up the toolbar buttons, the spinner buttons, the notebook tabs (still needs work) and also edited the gtk2 component of the theme. Because of that, I'm now calling this theme "elegant blackle" and it will be a remix of the original elegant brit theme in an effort to smash the gtk2 and gtk3 themes into congruence.
UPDATE (July 17th 2012): Finished fixing the notebook tabs, made the scrollbars, sliders and progressbars match the gtk2 theme.
UPDATE (July 18th 2012): Did some work on the check and radio buttons, Integrated [link]
into the theme
UPDATE (July 31st 2012): Fixed the way buttons show up in rhythmbox 2.9 (forced text under icons)
TODO: Fix the check buttons, radio buttons and comboboxes