It's busy has heck; trying to buy milk here on a Saturday while navigating the narrow aisles past shopping carts and baskets is like a game of stand-up Twister. Come at quieter times so you can soak in the organic hippie / poor portugese vibe and poke into all the corners to see what bizarre foods you might find. The prices are super cheap, but watch the expiry dates and age of the produce because you might not have long to eat it. Their stock rolls over fast and they're likely to be out of something you're looking for, so expect to make do.
The asian market further up St Laurent is a good alternative if you don't feel like pushing your way through the crowds at Segal's.