We had a lovely stay at Waikomo Stream Villas! The unit's much more spacious than I was expecting from the pictures. It was very clean, equipped for cooking, and well-positioned for the breeze, which easily kept it at a pleasant temperature all day. The location is good, with beaches and restaurants within walking distance, and Waimea Canyon not too far away by car. (I'd highly recommend the nearby Cave Preserve, and a Nā Pali Coast raft adventure from Kauai Sea Tours if you're feeling adventurous.)
It's not obvious from the listing that you never actually communicate with "Parrish" — he's not a normal Airbnb host but founder of The Parrish Collection, a vacation rental company. Immediately after booking I received a message asking for my email address as their booking system doesn't work through Airbnb messages. After some back-and-fourth with them and with Airbnb support (who confirmed that this is legitimate despite the help pages saying only to communicate through Airbnb), I gave them my email address and then had to complete a couple of forms to confirm the booking. (This included giving the names and ages of everyone staying in the unit.) The Parrish Collection staff were very responsive to Airbnb messages, and this was never a problem, but it was disconcerting and awkward. Also, one of the reasons I like Airbnb is because I know most of my money is going straight into locals' pockets, which I'm not so sure of here. That said, we had a great time, and I'd definitely stay here again.