Interesting idea. Well put it on the list of things I should try some day.
After a quick look at the site, I like the idea. But I wonder where it's limitations start to get in the way.
How about security, if I can modify the page, who else can? And who controls that?
How much code and logic does it handle before getting difficult to maintain? And how much data?
If I make an useful app with it, say to track beers, can I share the app with other people without so they can track their own beers, without sharing my personal data?
1. Security: It operates under the same security model as most website builders (think SquareSpace), we completely trust the end user to modify their own site in their own best interest. If the end user violates this trust, they will lose access to their paid account and could be liable to damages from other users. Their actions, their consequences.
2. Who can modify: You can modify any app you create. You can also "enable signups", which allows other users to easily fork your app, but they all trace back to your source app. We're making a plan right now where you can ship updates to forked apps.
3. Difficult to maintain: Pieter Levels (of NomadList) famously codes his $60k/month apps in single index.php files, so I suppose it matter how you organize your code and what level of navigating-through-the-cruft you're comfortable with.
4. Other people can fork your app and track their own beers. We also want to integrate collaboration features, so 2 people can have control over the same page simultaneously, but for now it's best for single-user apps.