I won't comment on the food because I didn't have the food at Imadake. Anyways, I've never had "real" Japanese food, so I wouldn't know how or what it should be. Others with me seemed to be enjoying the food though, so it was probably good (I will sample it soon, and update this review if I don't get too lazy).
But where Imadake scored big is with the Sake Bomb. A Sake Bomb is the Japanese version of the Irish Car Bomb: it's simply a shot of sake dropped in a glass of beer. But it's the whole ritual around the Sake Bomb that really makes Imadake stand-out: the waiters and the patrons around you get involved, and basically make you shout and bang on the table until the shots of sake, placed on two chopsticks on top of the beer glass, falls in the beer glass because of all the table banging. If you don't believe me, check-out the wiki entry for Sake Bomb.
Because of this amazingly fun Sake Bomb ritual, Imadake turns into this screamingly loud and fun bar at night. Hordes of Asian girls yell and get generally rowdy around tables packed with Sake Bombs, giving the place a distinctly different feel than the traditional Irish pubs that we're used to in Montreal.
What's more, the décor is simple and elegant (and feels Japanese too, but again I wouldn't really know). I especially love the large wall in the basement where you can let your imagination run free and write or draw anything with multicolored chalk.
Finally, the staff is friendly. Ask for the "sexy granny", she's a very good waitress.
I can't recommend Imadake enough: it's a perfect place for a loud and crazy, Sake-Bomb-fueled, Friday night, a place where you can escape from the traditional pub feel and enter a world of unknown Japanese mysteries.
PS: Imadake definitely feels more authentic than Big in Japan. Even Imadake's unusual physical location, on St-Catherine and Atwater, makes the place more interesting.