If I were going to try to make Bubble sound sexy to a developer, I’d say something like:
Bubble is a json-based declarative language for web application assembly. It’s designed to let non-technical users combine hand-coded javascript modules seamlessly into a working node.js application. It supports both front-end javascript components that the user can combine in a free-form way, and back-end server components the user can link together. It includes a simple but powerful expression language for linking components together and defining business and display logic.
I think @potentialthings is exactly right about making developers comfortable: the more that they can program things that plug in to Bubble, the more they will like it. Right now we have our API, which I think is a good selling point, and letting users build plugins is one of the big projects we have on our roadmap for this year.