Yes...GO! We enjoyed it!!
http://www.castleintheclouds.org/

People seem to enjoy visiting the place: http://www.tripadvisor.com/Attraction_Review-g46168-d558693-Reviews-Castle_in_the_Clouds-Moultonborough_New_Hampshire.html

HTTY

Castle in the Clouds was pretty cool! Save time to do some hiking there.

Thanks, we're on vaca in the White Mtns and I saw this thread yesterday am, so Castle in the Clouds became our day's activity.
We had our kids in 20's and teens, boyfriend, and my wife; we all thoroughly enjoyed the visit. Well worth the money with all the things to see. Waterfalls, mountain views, hungry salmon to feed while you eat an ice cream cone, gardens and one of the nicest homes I've ever seen. You can wander through at your own pace, very few 'red ropes' stopping you from exploring, and the guides that were scattered throughout the house were friendly, letting you sneak out onto patios and check out the attic so you can figure out how the skylight system was set up (the skylights were plate glass shining into the attic, with only diffuse light coming into the second floor through stained glass and opaque windows. Very clever and much easier to spot and fix leaks.)
My wife and I rode the motorcycle down from North Conway while the kids took the car. On the way back I was on my own so took the long way back through Maine.

A wonderful day, again thanks for the tip! Everyone is digging the White Mtns, Dad picked good!

bdokeefe,
I'm glad to hear you enjoyed the visit. I still hope we can work it into our trip next month! How long did you spend there? We'll be on our way from the Bretton Woods area to Boston and don't want to arrive in Boston too late because we'll be returning our rental car at the airport and then taking the T into the city.

We took our time, walked to the falls, etc and were there about 3 hours.