I played at Ko'olau three years ago and I can personally attest that it deserves every bit of that slope rating. It's hands down the most difficult course I have ever played. The course is carved out of the jungle basically, so if you spray your shots at all, kiss your ball goodbye. I'm an 11 handicap and lost at least 6 balls that day. A Scottish fellow I was paired with blew through a whole dozen in 7 holes. He had to get a marshal to go get him more.
The 18th was a prime example. It played about 450 yards with long forced carries over the jungle on your drive and the second shot, with thick jungle left and right about 10 yards off of the fairway, and a string of deep bunkers on the right hand side of the green and the runup to the green. It was target golf the whole way around.
It's a beautiful place though. It runs along the bottom of a rocky mountain range (the one they show all the time on that ABC show "Lost").