We haven't done it recently, but we did it in 02. Very nice, yet they do increase the price, if I remember correctly, over the couples massages offered on the ship. All in all, at the $300 plus price tag, it was a nice thing to do for our honeymoon, but I doubt we'll "invest" in that again.
We did do a couples massage on the ship on our last cruise....I can tell you, the massage was just as good as the cabanas, but obviously, the atmosphere is not there, but the end result was certainly the same!