We always get park hoppers, so there's no such thing as a "wasted" day cost-wise -- if we run out of things to do at a park, we leave and go to another. Even if I was stuck doing one park per day, though, I can't imagine skipping HS. Tower of Terror is my favorite ride in WDW (quite possibly my favorite theme park ride in the world), and there's enough else to do there that I've never felt like I went there just for that one ride. It's a small park, to be sure (I worked there on the College Program, and my supervisor used to say "this park is the size of a cardboard box," and she was right -- it's actually even smaller than it feels as a guest because it's built to be a bit maze-like), but I love the theming and what attractions it does have are at the top of my list.