I have to repeat what Michael said previously. He took the words out of my mouth.
The Atrium is located inside Les Cours Mont-Royal (shopping mall) on the first floor. It has two parts - a small dining area and a lounge with comfy seats. The lighting gives the lounge a nice ambience and with wifi, makes a great place to hang out and work.
I found the lunches to be extremely fresh. I recommend the Thai wrap. Even the coleslaw (which I'm never a big fan of) was fresh and tasty. I've never had dinner here, but now I'm curious.
What's nice about the Atrium is that you can get coffee, tea, and meals all day, and they even have a bar, if you're in the mood for a glass of wine. The staff are also very friendly.
The place always seems empty, so it's quiet and private. I would even consider it a good casual date spot, for young people on a budget.
It's a quiet oasis in the middle of the city.