Has anyone else tried this? Personally, I think it's almost as valuable as Scrivener (same developer).
I have a very similar application for iPad called iThoughts. I used it for a bit then realized it wasn't a fit for my process.
I've taken a look at Scapple one or two times, though considering the fact that I have pretty much no idea what it is I think we can conclude I wasn't particularly interested.
I will add that people for whom Scapple is a process fit seem to really love it. I belong to a couple of Scrivener groups in various places on the web and Scapple users are usually very huddled and intense concerning making use of it. Not unlike Scrivener users, in a way.
If you don't use Scrivener, there are probably free alternatives to Scrapple that you could find online. Mind-mapping software and similar tools. If you already use Scrivener and find this sort of thing helpful, it's probably worth the $15 because of how easy it is to import the end product into Scrivener.
@Wreybies, as requested, this is one way to use Scapple, demonstrated by analyzing an easy, well known film, The Matrix In scheme ONE, I'm just throwing out the main characters, and drawing relationships between them. Thus, for instance, Morpheus and Neo are linked. In scheme two, I'm beginning to explain those connections. Morpheus awakens Neo from the Matrix. Trinity loves Neo. In Scheme three, I'm starting to think a little more. I'm fleshing out those connections, and I'm also searching for patterns (visually). So, Morpheus is a Greek god of dreams, and he awakens Neo and the others. Since I've seen the film, I know these characters are essentially being "reborn," which is definitely a religious concept. So is the holy trinity, and the oracle is similar to Morpheus in its Greek origins, also the quote "know thyself." So I can lump these all together into "mythology." Now that I'm starting to find patterns, I want to flesh out my other bubbles, see what else, again, visually, is important here. So in scene four I start adding stuff, but only things I think are significant. Well, what about setting? Most of the matrix takes place in an American looking city. Then we have Neo's cubicle. Finally, in scheme five, I've created more "big" categories, or major themes of the movie, and linked them to the actual story elements. Thus we have mythology, faith, freedom, science, illusion and slavery. I'm sure there are more. We can use the connections to get more specific. Arguably, based on this scheme, one of the themes is the dual nature of science or technology. It has enslaved mankind, yet the rebels are completely reliant on it. Another major idea in the film, which you can get from the last scheme, although if I wanted to spend more time I'd probably draw it out more visually, is the idea of knowledge, and how we get it. There's the "faith vs science" angle, drawn out here, but also, based on the "illusion" bubble, we can see it gets more existential than that. These connections may seem obvious, which is why I picked this film, but imagine you're doing this now for your novel. My guess is mapping it out can help you realize some significant themes, and or draw them out more. It's certainly done that for me. edited to add: The value of this is at least four fold. 1. It allows you to define your characters in a more flexible, functional manner, as opposed to some silly character sheet. 2 It reveals the themes in your novel so you can help crystallize and expand them in your next draft. 3. Seeing what your novel really is about allows you to replace fatty, empty parts of your work with more relevant and meaningful content. 4, and perhaps most importantly, it helps you make your novel be more than just the sum of its parts.