Studio 11 offers an awesome yoga experience. The instructors are very knowledgeable and love teaching. The $33 new student pass good for unlimited yoga for 3 weeks is definitely a great way to try out different classes and instructors. Their monthly passes are reasonably priced too considering that they offer classes every day of the week and at various times every day. They also usually have a 3 month pass for 2 months' price promotion going on which is a great deal.
I really like the fact that most instructors at Studio 11 emphasizes the spiritual aspect of yoga and do not treat yoga as a mere weight-loss exercise. Many instructors are massage therapists and/or chant artists themselves. They also offer great Pilates classes as well. I think yoga and Pilates complement each other very well. I really need Pilates for core strength to go with my yoga practice.
The studio is gorgeous and spacious (2 floors). It's located in the 100-year-old Lemko building right by Lincoln Park in Tremont. The coolest yoga studio I've ever been to.