This app-store-only app is a no-frills outliner that has some appeal compared to some other outliners that have a non-trivial learning curve. However, it has its own storage system, akin to Apple's Notes app—no Finder integration which has been the standard since 1984. This is even worse than a proprietary file format. I'm not too worried about being left with inaccessible Notes files because I assume Apple, as a company with a lot of users, would not do that. However, I have no such faith in a small developer. I've been burned before. Zavala should use OPML files as its default, not just as an export option. And there is no folder concept, only tags. While this can potentially be better than folders in that a "file" can be in more than place without making aliases, it is not a workflow that many are accustomed to and which eventually takes more attention. OmniOutliner Essentials is not as no-frills as Zavala but still easy to use, and with a traditional file model.