Ever since I upgraded to Ubuntu 12.04 I've somehow managed to keep my Desktop look nice and clean with Dark context menu and nautilus sidebar.
I recently installed 12.10 on my laptop, and after using it for a while I realized the default ambiance theme is inconsistent. Some apps had dark context menus and dropdowns and some had white. So I went about forking the default Ambiance theme to make it look a bit more consistent and pretty.
To use the theme download the zip file from the download button below and extract the theme folder to home/.themes folder, If you don't have a .themes folder go ahead and create it. Then use the Ubuntu tweak tool or My-Unity tool to change the theme to com.solancer.ambiance.