Scotty's castle is interesting only because its a spacious house in the middle of the desert. However if you need to sacrifice a few places to make room for others this is it. Do stop and take a few pictures but the only reason I would recommend taking the tour is if you're traveling with children, they may find it interesting but for a more adult audience the tour is not as impressive as the rest of what death valley had to offer. Keep in mind that you can't walk into the house without taking the tour. Your choice. If you do decide to take the tour, there are plenty of people who like them, so search in the “Things to do” section for more info
Given the cost of gas, I think Scotty's Castle is a waste of time. This summer retreat of a wealthy Chicago Businessman is nothing more than an incomplete architectural structure built because of the lure of Scotty, a local who conned people into investing in land he supposedly owned that had gold. Based on this lie, he convinced this Chicago businessman to invest in a summer home which Scotty lived on.
There are two tours you can take. Whatever you do, avoid the tour of the basement of this "castle." I was so bored by the tour that I nearly fainted. Although the tour of the castle is interesting, I regret wasting the 1 hour and 30 minute drive to get there from Furnace Creek. I would have preferred to have visited other places such as the sand dunes, the Devil's Racetrack, which is an amazing marvel of gigantic boulder's that appear to be racing each other each with "tracks" caused most probably by its sliding on the icy ground during a colder than average winter.
Unique Suggestions: Climb up to Scotty's "grave." There's at least a nice view.
Fun Alternatives: In your list of things to see in Death Valley, rank it 7th or 8th.
They have you trapped here, yes? Yes, it is hot here. You need to take water on your exploration outings. Boy do they have you now! Bottled water is overpriced. It is highway robbery as we might say in the U.S., and the spigot water has a poor taste.
Fun Alternatives: Bring lots of water with you. Fill up large jugs at home or buy bottled water before you come to the park, and bring one or more smaller bottles you can refill from your jugs. These smaller bottles will be the ones you will carry with you when you go out hiking.
There are not many gas stations in Death Valley. But the one at Furnace Creek is very expensive...the prices can easily reach over $2.00-2.50 a gallon. So come to Death Valley with your gas tank full. You'll need it because it is the largest national park in America. And it's a good idea anyway to keep it full in the hot weather; if your car runs out of gas in the middle of the desert, you're in big trouble.
(Actually I wouldn't call this a tourist trap, since the high prices of gasoline is understandable because of the location in the middle of a desert and the cost of transporting the gasoline. On the other hand it is a trap since when you run out of gas, you have no choice but to fill up with this expensive gas.)