As others have noted, booking flexibility and same-day changes are the key to success in using GPUs effectively.

Note that the W fare bucket or up only applies to intercontinental flights, not North America or Hawaii. Also note that Q and V buckets can actually price lower (in the $100 range) than W on some TPAC or TATL routings. I always search for Q,V,W fare buckets to see which provides the lowest fare .

My preferred approach is to book one-way itineraries (where there isn't a price premium) to insulate same-day changes from messing up down-stream flight segments.