There is an other-worldliness to some of her melodies, and they are sung in a delicate, lilting voice that is really strong. When singers like Bjork or Janelle Monae are able to impress by their sheer range and emotional range, St. Vincent does the opposite-- she impresses by possessing an incredible voice but refusing to show it off.
She's pretty theatrical, which turns a lot of people off. But i definitely appreciate the comprehensive approach: music, image, lyrics, production, execution. One could also call her narcissistic, but eh... what singer-songwriter isn't, really?
Definitely worth listening to, and recommended for fans of left-of-center indie pop songwriters, or fans of Sufjan Stevens, My Brightest Diamond, Neko Case, et al.