I have sessioned with Mistress Yin twice in New York.  She is a fantastically intelligent and creative dominatrix.  She is an Ivy League graduate.  Sinuously attractive, the original "Dragon Lady". Absolutely no sex whatsoever, like all professional dommes, but fantastic.  Check out her reviews on www.maxfisch.com, the BDSM website.  She has an amazing professional life, as she travels frequently for days-long private sessions.  I understand she is a "needle" expert.