A cool, artsy place where tons of Montreal-ites and tourists gather for local festivals and events. When I was there this past weekend, they had a comedy/music festival going on. Tons of food trucks lining the streets, lots of young people milling about, brightly lit with strange sculptures lining the walkway (enormous desk lamps and flailing octopus tendrils), people in costume, etc. It's a nice place to walk around a bit and maybe food tour the food trucks around (though they're usually overpriced versions of restaurants around the city), but otherwise, it's not all that exciting a place unless there's a great festival/event going on. It's probably a really fun place during the winter holidays or national holidays.
Down some of the side streets, you can find some nice bars/pubs, like NYKS. Lining the main boulevard though are all chain stores and fast food joints (ie. the large McD).