I've been going to Green Tara for over a year and while all the teachers at the studio are very good, Karen is by far the best. She is an excellent instructor who is disciplined and emphasizes form, teaching you to be thoughtful and aware of your body. What really sets her apart is that she is both yoga teacher and life coach in one, without being too self-help or corny or inaccessible. I'm not at all new-age-y, but her classes really transcend your traditional pose/ stretch/downward-facing dog, and leave you with both a refreshed mind and body.
The studio is small but cozy, and you get a feel for a sense of community as the classes are a good mix of long-time veterans and first-time drop-ins. I've also taken some classes at the Yoga Room which is an amazing facility in one of the converted Little Italy school-houses, but the quality and the level of detail of teaching at Green Tara in one of Karen's classes is unmatched.
I've only ever done Iyengar yoga (minus the yoga class I went to at a 24hr Fitness once, which was so UNNATURAL and weird), so I can't compare it to any of the other yogas, but the perfectionist in me loves the slower pace and an almost cerebral emphasis on form. Check this place out!