We went to the Luau just on Oct 1. It was good, something to see once. We took our 2yr old dd w/ us and she loved the show. The food wasn't as good as I hoped, after eating at 'Ohana's two nights before I don't think anything could've compared.
We'll probably skip it the next time we stay there but it was something to do once - Personally, I think ohana is much better! (And not much cheaper for two adults and a couple of drinks).