There is some good informational stuff here. It would be great for bringing a kid for that reason. I liked the climate change simulator game, which had a model of Montreal that changed colors based on your answers to various questions. The main thing here though is the nice viewpoint and nice breeze.
The outside is actually just a metal frame so you're exposed to the open air. There used to be an acyrlic shell but it caught fire. There's a picture of the Biodome on fire on the wall in one of the hallways.
From here, you can see downtown, the old port, a little bit of the hairpin at the racetrack, and then out towards Longuile.
There is construction going on here. I recommend taking the subway anywhere in Montreal that is near one, but this is an especially good place to subway to.