I went there about a year ago for an aviation law conference. (I'd been a few times before too.)
They had us take a tour of the Canadair factory which was an amazing facility. I'm not sure if you can get a tour if you aren't affiliated with the company however. There are also Textron factories in the surronding area.
Besides those factories, the city is awesome, especially in the summer! The girls there are beautiful, the food is good and nothing is too expensive.
The night life is also pretty amazing, but it is a bit tuned down from NYC, which I like a lot. I would aim for the hip areas just to the east of the Mountain. That's where I tend to stay when I visit the city. Speaking of the Mountain, be sure to climb up the thing if the weather is clear, it's a fantastic view! The old city is also kinda cool, but tiny and touristy, so it's not really worth more than an hour or two of walking around.
Be sure to visit the museums, especially the muesuem of canadian art, which is designed by Safdie, and is a beautiful building. The island in the middle of the river is also worth a visit.
Oh and if you speak French, prepare to be confused. I have a lot of trouble making out the Quebec accent, although the people there seemed to understand me just fine.
Have a blast! It's a great city!