Spectacular, beast of a hike. Started from the west (FR 610) trailhead, reached Nankoweap Creek by mid-morning. You don't want to be starting the climb back out in the heat of the day, so I wandered slowly down to the Colorado and back, stopping frequently to eat, drink, rest and soak in the gorgeous water. I had visited the granaries on a raft trip a few years ago, so I didn't feel the need to hike up and see them again. Waited until about 4PM to start the climb out, reached the park boundary by nightfall and finished by headlamp and moonlight. I'd rate this as easily the toughest GC hike I've done yet.