Pretty simple idea. Good execution. Good UI / UX apart from some texts which are hard to read.
It's unintrusive as in you define and style your own form, but this also means you have to style your own form. It would be great if the platform provides a form builder, so people can use it to compose their frontend code as well. Then there won't be a need to write frontend or backend code.
The configurator allows total freedom in building your calculator, which comes with a slight learning curve. Once you've mastered it, you can build very sophisticated and powerful calculator forms. And even integrate quick checkout and payment.
Support is excellent, so you will always build what you have in mind.
And the product receives constant updates, so they're working hard on making the current experience smoother and adding additional features. I'm very excited about the product roadmap.
All in all very solid product that delivers on promise.