The Oasis rooftop bar at Gretzky's has a great atmosphere -- I like how it's hemmed in by so many buildings, giving it a real downtown feel -- but otherwise it's nothing spectacular. If you're from out of town and visiting the city for Jay's game, this could be a good experience, but if you live in the GTA, I wouldn't bother.
The beer was reasonably priced (they have specials), but the food is expensive and service was slow. The seating is also a bit cramped.