We always rent from Alamo Car Rentals when we go to Kauai. The pick up point is at the airport in Lihue. You have to take a shuttle bus from the airport to the car rental, but they run every five minutes or so and when you land in Hawaii, somehow time becomes irrelevant anyway! But once you arrive at Alamo, everything is so easy! They have a kiosk for super fast checkout or you can get personalized service at the counter. The clerks all seem to have that Aloha spirit, which keeps us coming back there. Well, and the prices are always the most competitive we have found.
My place of employment also offers us a discounted rate which helps quite a bit. We have discounts on the other car rental companies too, but every time we've planned our vacation, Alamo wins in the pricing category.
One year my husband didn't like the car we rented, so the following day we returned it with no problems. They just had us choose a replacement and off we went!
Between service, price, and quality, we have been completely satisfied with Alamo Car Rentals on the island of Kauai.