Unlike the other reviewers here, I don't use this duo for smokey eyes. Instead, I prefer using both colors to layer crisp, clean lines for a dramatic (but minimalist) retro-styled look with a winged tip. And the styles of application provide plenty of opportunity for variation. I've layered top lid only with black under white all along the lid to a slight wingtip, black outer lid with a white inner lid, black top lid with white along the lower-lid waterline, or black and white sweeping in opposite directions along the upper lid, not to mention either/or on their own.
Although significantly trickier to apply than a no-hassle liner pencil, this is easily the smoothest and cleanest cake formula eyeliner I've yet tried. With a good application brush and a few practices tries, it shouldn't present too many problems for a new user. Highly recommended.