I can't say much beyond what others have already said. Go once for the experience, not the food. It's pretty standard wedding-style prix-fixe food that is executed adequately (it's not bad food; everything tastes fine). I've been to both Toronto and Montreal locations and can report that the quality levels are essentially equal.
The experience itself is fun though! The wait staff are good at making sure service happens with a limited amount of fumbling and tumbling, and it's very cool to give your optic nerve the night off and see how that affects not only your experience with food but with your companions as well. I recommend the surprise options for the courses to maximize the experience.
I have to say that it's a shame that O. Noir doesn't fancy itself a purveyor of truly good quality, interesting food, because think of how cool it would be to get surprising flavors and textures and process all of that using only your sense of taste? It is as if the owners think to themselves "but we're already putting them in the dark--why risk alienating people further with unfamiliar food?"
I understand that perspective, including the many logistical factors a place like this must have to consider that no other restaurant has to, but the last time I checked, not every really interesting menu was full of jarring items like offal or horse meat. I actually think people would flock to a place like this--more than just once--if there were a creative chef at the helm who could provide seasonal menus that would really make use of the in-the-dark concept.