Great views of Calgary and the surrounding areas, especially on clear days. You can see for miles and miles because most of the Calgary landscape is very flat. If you arrive in the evening, you'll want to stick around for the fab sunset if you can wait that long.
Enjoy the glass floor area. Similar to the Step Out Ledge at the Willis Tower in Chicago (formerly known as the Sears Tower), you can walk out onto a shelf where the only thing between you and the street below is a thin piece of glass and 525 feet of air. It takes a little courage to do it, but it's an awesome picture!
Souvenirs (of course) at the top and at the bottom. Priced reasonably.
Looking at the history of Calgary, it's sort of sad that this is no longer the tallest building in the city. Bummer.