The Na Pali Coast and much of the interior of Kaua'i are inaccessible by ground vehicles. And many of the really scenic parts of the island are only visible by air. So a helicopter tour of the island is worthwhile. You'll see jagged seacliffs, spectacular waterfalls and follow twisting canyons as well as fly into Mount Wai'ale'ale's crater- a box canyon with waterfalls cascading down the 3000 foot sides.
Flying in any helicopter is an adventure for most people. But this heli tour is even more exciting than the others, for several reasons:
1) Inter-Island is the only company to use the Hughes 500. It seats 4 passengers, rather than the 6 passengers that A-Star and Jet models carry, so you need not fear being stuck in a middle back seat. The Hughes 500 is smaller and more maneuverable, so you should get a more thrilling ride.
2) They fly with the doors OFF, unless otherwise requested. That's right, should you lose grip on your camera when the 'copter is banking, you might watch it plummet to the cliffs below. Aside from upping the adrenaline factor, you will have greater range of visibility and no glass glare in your pictures.
3) For their 2 hour tour they land at a waterfall in the remote interior (not reachable by any form ground transport, including hiking) for a mid-trip swim and lunch. This is the only company that currently offers a mid-trip landing.
Of course, helicopter tours are expensive, noisy and not inline with low-impact, fuel-efficient ecotourism, but a flight over Kaua'i is a guilty pleasure even die-hard, penny-pinching environmentalists should allow themselves, at least once.