My wife and I went to the Castle to celebrate our 25th wedding anniversary and couldn't have been happier. The stone work and architecture of the castle was breathtaking. Every little nook and cranny was thought through. It is a work of art in a way!
Then there is the view! The trip up the long drive is worth it. Being on top of the mountain, everywhere you look is pure beauty and it's so private.
We liked being on the east side of the island away from the more busy Cruz Bay area. It felt more local and there were a lot of less populated interesting beaches i.e. Francis Bay, Maho Bay, Salt Pond Bay, Drunk Bay etc.
I would recommend going to the Concordia restaurant. It overlooks Salt Pond Bay. They have a great food and an open mike night on Monday :)
Overall I give the Castle two thumbs and would recommend it to anyone who is looking for a private getaway on the most beautiful island I have ever visited.