This is a long, meant for "hikers" hike, not for the average couch potato who wants a basic route. The elevation change (overall) is only 400 feet or so, but you do it SEVERAL times—sometimes on continuous steps (over 200), and sometimes on muddy slopes or rocks (where you CAN slip). Part of the swamp trail is boardwalked - to help you avoid the wetness and to protect the swamp. Much of getting to the swamp is NOT boardwalked - and still muddy in places.
The reward is what is considered the "most unusual hike in Hawaii"—that would be hiking through the world's highest swamp and the diversity associated with it (and getting there)—and a gorgeous view of Northern Hawaii, including Hanalei Bay. The reward is worth it if you have the time for a longer hike and are up to the challenge.
You start by a boring hike along the (ex) road (1¼ mile) to get to the beginning of the trail... while pondering WHY they had to close the road. At the end of this part (a part MANY people opt to do) you get a really nice view of the Kalalau Valley. Then it's off on the Pihea Trail (2 miles) which takes you along the valley and through forests of ferns and ohia trees. Some of this is steep ups and downs. Little of it is boardwalked (towards the end it is).
After the intersection of the Alakai Swamp Trail you head east (2 miles) and reach the end of the trail at a steep cliff. The route passes through the swamp - and two long sets of steps - one that is VERY long. There is one water crossing here, but when we went it was easy to get across without getting wet. The trail is boardwalked through most of the swamp. You've lost the forest... but gain the swamp plants—and some OLD power poles—leading to more "wondering" questions.
The end has an awesome view; bring snacks, drinks, sit (there is a small bench), and enjoy. We saw clouds literally blow in, and out, making the view go from fantastic to nothing, and back. It was really neat to see. Plus, if you first get there and see the "nothing" part, just wait a little bit. It can change quickly.