We had a great experience with Botanical World Adventures' zip line on the Big Island in Hawaii. The experience lasted roughly 2.5 hours. The staff were courteous and well-informed, the equipment was in excellent condition, and everyone was well-organized. Roughly 2 days before our experience, the company will email a reminder to complete your waiver online (which was easy to do) and provide directions. They fit you with your gear and then drive you to the first zip line. You walk between each zipline, but are driven to the final zipline, which was a stunning finale, as it was a half mile in length as you soar past a waterfall with the ocean as a backdrop.
Other bonuses: The ziplines are in an area with a great deal of botanical diversity so our guides pointed out different plants and trees. Our guide picked fruit that was edible. Finally, they took pictures and sent them to us a a few hours after completing our zipline experience, and we were able to download them for free! (instead of having to pay for them like some companies do). I really appreciated having these photos with the whole family.
The only drawback (and it is minor) is that that the only restrooms are the portable restrooms. They have 4 of them, which was helpful as there were 15 people in the timeslot that we zipped in. But when you're traveling, I'll happily take a portapotty over no bathroom.
Bottom line: Great customer service, outstanding guides that were knowledgeable and respectful, safety is #1, and we had FUN! You zip over beautiful scenery with the ocean in many views. Who could ask for anything better on the Big Island? I would return and repeat this experience.