Aww, I liked the Biodome. If it's only taking less than an hour to get through, you're going too fast or perhaps you've been here before. I enjoy just standing in each ecosystem and looking in the trees, air or water for whatever creature comes springing or gliding into view. My favourite section is the underwater observation tank in the St. Lawrence Marine Ecosystem where you can actually watch these huge fish swim and familiar birds dive and paddle just inches away from you. It's very hypnotic and I enjoyed just parking myself here for about 15 minutes.
In all, there are five ecosystems that you're usually a part of, so the shift between exhibits is cool. If you want to put down the extra dough, you can also see the Insectarium and Botanical Gardens ($27 for adults). If you're a student, senior, Quebec resident or child, you'll get a hefty discount.