I also use the "painted black - forms" style http://freestyler.ws/style/3198/painted-black-forms

EDIT: I'm actually now using http://freestyler.ws/style/14136/torrentz from Dzon65@userstyles which is based on my style but looks really better and is still dark.
EDIT2: oh well the style }entionned above is now obsolete, so this one's back in the game! ;)

updates:
20100627: fix colors in the results "header" + visual sign to show which sorting is currently in use
20101222: add torrentz.eu