This is a Montreal institution, and an essential part of the Montreal experience. Do come here, sit at the counter and order a smoked meat sandwich (medium of course) with a cherry cola. Look around at the crowded tiny space, and soak in the atmosphere.
Once you have gone once, and have experienced the great smoked meat, and the overall craziness that is the Schwartz experience, I would suggest sticking to the Main across the street for equally good smoked meat, and booths where you can sit and relax without bumping elbows. Also beer.