I walk by it every day and am still always staring up at it like a tourist. The diamond pattern does two thing very well:
It makes it look amazing at sunset as the light is catching it from the west.
It helps offset the transparency that even the best curtainwall experiences at peak sun. A flat facade like Bay Adelaide can look rather lacklustre if the lighting is wrong.
from:
https://www.flickr.com/photos/jacklandau/30763188795
With the diamond pattern, there's always a portion that's reflecting in a much more flattering way and drawing attention away from those that aren't.