My wife and I ate dinner at Steak Frites while visiting Montreal the week after Christmas, 2010. When we arrived at about 6:30, the tables were starting to fill up. Although we didn't have a reservation, we arrived just in time, as we ended up waiting only about 15 min. while several other couples and groups arrived just a few moments after us.
We're both fans of great (read: medium-rare) steaks, and they didn't disappoint. We shared the 10 oz. filet mignon - "for two" as the menu says - for about $52 Canadian. The meal was served with warm bread, a large bowl of salad, and bottomless fries. We also recieved three kinds of sauces, each of which were tasty with various flavors.
Most importantly, though, you should note that they don't serve wine, so stop by a local liquor store and pick a bottle up beforehand.
The restaurant was highly recommended to us by someone we met at a spa in Burlington, VT, and Steak Frites did not disappoint. Just be sure to make a reservation!