From a product perspective it has potential, but I don't see it (at this moment) being used to build nothing more than simple applications (their case studies are simple CRUD apps).

The Scenario Builder is not easy to understand (you need to define a data structure to serve as a contextual variable) and it's really limited to what you can do. There are simple things that are missing like For loops or While loops to create logic. Passing the output from one step to the next one is done only thought the context (again, not so easy to understand/use).
You can't use the JS SDK (Action/Condition) which gives you more flexibility because it's not included in the deal.

Plugins - At this moment plugins are very limited in terms of what do (extend the platform), they are just a wrapper for http requests (you can simply call an external API, that's it - the same thing you can do with the HTTP-request Action).

The web pages (frontend visual builder) is just an MVP (in my case I don't see the point of using it at this moment).

Looking at deal and the plans offered it's very difficult to evaluate if it's a good or bad there are so many restrictions/limits, the biggest problem for me is that I can't use the on-demand resources/billing so investing in advance without the possibility to take advantage of the AppSumo plan is nonsense.