Stupendous scenery--after a lot of pain.
Only attempt this as a day hike if you are experienced in hiking and in decent shape (otherwise take a helicopter trip in). DOC claims an 8-12 hours return--this for a ~12 mile (19 km) return. Yes, it really is likely to take that long; the net elevation of gain of ~1600' (from 380m to 880m) requires you to ascend a total of 2500' (760m)--after the first 200-250m gain, you literally are taking two steps up and one down. The trail sidehills through southern beech forest, in places being very narrow on a steep slope. We lost count of the number of downed trees we had to go over, under, or around. The trail crosses numerous landslide (slip) scarps, making for quick steep up-and-down sections of trail. Other than some large trees, views in the forest are rare. Eventually the trail descends to near the stream, indicating you are getting close. After crossing a tributary which descends in an open area you have about 500m to the bivouac as shown on the map; this is where you emerge from the forest. A walk of ~1.5km brings you in view of the glacier and falls at the head of the valley (this is the 6 mile point); you can go farther to see more. The trail saw a total of 11 hikers on a February weekday; several had spent the night in the valley. That might be the best way to visit--you don't immediately face the daunting prospect of the descent through the trees to the trailhead. My ranking of 7 is balancing the great scenery at the top against the miserable trail up to it. Note on trailhead: the DOC trail starts on the far side of a farmer's pasture off the Lovers Leap road on the east side of Earnslaw Burn; we and several others parked on the side of the road in the grass there, but I don't know if this is permitted. A local claimed you could bushwhack up the west (right) side of the stream from the end of the road in the national park just right after crossing the Burn, but I suspect this would be very difficult