I've been to Paradise Cove twice; once when we lived on Oahu (and our friends had extra tickets that the couldn't use so gave them to us) and once with my friend and mother when we went in 2004. That was one time too many!
The first time, it was fun, since we had just moved there. LONG drive home, since we lived in Kailua. We were exhausted going home!
Second time, fun for the activities a little. Then the show, well to me it just goes on and on. I live on the East Coast now, so with the time change, I was just falling asleep. It is a LONG evening! Food - don't go for the food. It's basic luau grub. Drinks - I stuck with beer. They use the cheapest alcohol known to modern man. I mean stuff I had never heard of cheap.
As far as luaus on Oahu, it's probably the best. Nicest show, and lots of fun stuff to do beforehand. If you really want to go to a luau show and you're on Oahu, and have never ever done one, then I'd say go. If you have done one before, I would skip it and instead go see some good local Hawaiian music. The Crown just opened up in Waikiki and there are other venues for good Hawaiian music.