I've tried it out, registered for the premium to check out the details.

Biggest problem: querying Firebase is problematic. I can bind a collection to a ListView, but in many cases I'd like to map a field to something. For example I have a list of "purchases" and I'd like to map the "buyerId" to an email address. This can't be done, and the generated code is hard to adapt to this kind of use case.

And therein lies the complexity to be honest.

I think it'd worth $30 just as a designer. But you have to be able to code.