In order of importance:
The instructors are fantastic (and not pretentious, which is a huge plus for someone like me who is kind of terrible at yoga).
The class offerings are great – both the variation of classes (HVF, SHB, YogaTone), and the volume of classes offered. I sneak out of work early on Fridays to make it to Matt’s Sweat, Heat & Beatz class, because it’s just the best, and makes my week. Everything is better when I’m in that class.
The locker room amenities are a really nice bonus. I’ve taken advantage of the complimentary hair ties a few times.. Hot yoga without those would be less pleasant.