Joined OTF this summer, and wholeheartedly recommend - it's a great workout.
Beyond that, the staff is extremely friendly (I regularly see the instructor walk around and chat with members pre/post class), the equipment is top-notch and the facility is clean (nothing worse than a dirty gym)!
However, where they raise the bar is the lengths they go to ensure members are getting the best possible workout, in a way that's tailored to their abilities and injuries. From both personal experience and observation, the instructors are extremely committed to coaching people to get stronger and fitter in a way that is motivating.