As a yoga dabbler, I've been on a Groupon tour of yoga studios in the city since moving to Toronto. I have to say that I am incredibly impressed with Iam yoga studio.
The space itself is really stunning. It's spacious and welcoming, with lots of space to sit and chat with your instructors before and after class. They have an odd sign in method for Grouponers, as others have mentioned, but the desk staff are super friendly and check in is always fast.
The change rooms are fairly spacious, bright and very clean. Minor quibble- the lockers are a little bit small!
What is most important and impressive to me here is the consistent quality of instruction. I've tried 3 different classes with 3 different instructors, and have been impressed each time with the instructional quality. At other studios, I've found this aspect to be really hit or miss, so as I said, I'm very impressed! They also offer an impressive variety and schedule of classes.
Finally just a warning- their hot room is HOT. Like, really, really hot. Luckily they don't overbook their classes, so the room typically isn't crowded, but holy crap it's hot in there.