Any feedback?
Mindmaps get little traction imo because this first experience is usually dreadful: Simple examples (like you show) are just as well represented by a bulleted list. And complex examples need a really slick and intuitive UI, otherwise they are too painful to create.
My take on it is Markdown in a private Github repo provides 90% of the benefits and a lot of other features, with none of the worry about being locked in to a new company whose product is immature and doesn't have an established track record.
Finally, your posting those 20 free keys to the pro plan just reinforces in my mind the notion that the price-features balance isn't attractive.
An interesting idea, although a bit counter-intuitive: in principle, a mind map helps you to visualize ideas better, in a way that lets you restructure them, etc. This visual outlining process is a tool, not the end goal. You'd expect to start with a rough diagram of idea nodes, not with a list. That said, starting with text could be useful in some cases.