Otherwise known as ATP, Alberta Theatre Projects is a theatre company that offers a variety of plays, usually a bit edgy in nature. The programs take place in the Martha Cohen Theatre which is just the perfect size to create an intimate atmosphere in which to enjoy a play. (450 seats or so)
I doubt there's a poor seat in the house. I've sat both centre and on the extreme sides, the latter offering a great view of the stage, and I have never felt that I was missing out on any of the action. Sometimes the side mezzanine or balcony seats are better just because there are less people sitting in front of you than if you sat in the centre. (Actually some of the side seats are just one row, so there's nobody sitting in front of you.)
ATP offers the Playrites Festival of new Canadian plays each year in about February. You can see a bunch of plays over a two week period.