If you like vinyasa (or 'flow') yoga, Shakti Vinyasa on Market Street in Ballard is my top pick in Seattle. Studio owner Lisa Black was a long-time instructor at 8 Limbs in Wedgood before striking out on her own about a year ago. In a very short time, she's created a warm, welcoming studio with a great team of instructors.
Lisa's studio has a loose affiliation with well-known instructor Baron Baptiste, and her teaching style is similar, blending traditional yoga poses and discipline with a powerful, flow-oriented sequencing and pacing. Classes can be meditative, but you should also expect a solid, full-body workout.
Also, unlike some other studios around town, Shakti has great practice spaces - with high ceilings, warm colors and great light.
Finally, if you're looking for a good excuse to go abroad, Lisa also runs annual week-long clinics every February at Maya Tulum in Mexico. (See my article on traveling to Tulum to get my take on the area -- it's another personal favorite).