Royal Lahaina Luau in October 2011 and had a great time. The setting is during sunset, right beside ka'anapali beach: out-of-this-world gorgeous. The food was great and the hostess of the luau has a great sense of humor. In a kukui nutshell, a luau is a big feast (usually a buffet) and Polynesian entertainment. I recommend arriving early so that you can enjoy a mai tai (courtesy of an open bar) and see the imu ceremony (pig roast) before you take your seat. After you eat (the delicious array of Hawaiian cuisine), you are treated to a lively show of Samoan, Tahitian and Hawaiian dancing. It's really cool and certainly something you can only experience in Hawaii and should definitely do so at least once.
We hesitated on attending this luau after reading various poor reviews. The comments were that the drinks are watered down, and that you are served dinner with plastic dinnerware. After personally experiencing this luau, I can tell you that if the drinks are watered down, it would be due to ice melting. Our drinks were great and plenty strong enough. As for plastic, it is not the flimsy plastic you get with your fast food - this is plenty sturdy enough to enjoy your kalua pork! We took the opportunity to attend and I am glad we did. I loved it! This is the oldest luau on Maui and I wouldn't hesitate to recommend to anyone that they take it in and enjoy it for what it is - a feast and Hawaiian entertainment under the stars of my favorite resort in all of Hawaii. The food - delicious. The entertainment - beautiful and genuine. The location: Breathtaking. You couldn't ask for a better night under the stars.
You can also check out the also-awesome Old Lahaina Luau, but I will save that review for later!
PS I recommend paying the small price (I think it's $15) for an upgrade so that you can be admitted right away instead of waiting in-line and enjoy those mai tais AND you get preferred seating (though it could be argued there really isn't a bad seat).