Is it Production Ready?
Yes! Before Semicolon and this current website uses it with amazing results as far as loading time and consistency.
Does the tag code shipped to the browser?
No! Everything is Server Side Rendered. You can always pair HTML+ with client side render libraries like React. Some work is being done to allow client side rendering in the future.
How to make it refresh when I make changes
This is a feature in the works but you can always use modules like Nodemon to reload your server on changes.
How fast is it?
The HTML parser itself is super fast parsing big size html in couple milliseconds. The load time of page will vary by template and whether in production or not.
Can I use it with Koa?
Not yet. Koa support is currently in the plans.
How to fetch data?
You can setup express endpoints or Rest APIs or even use a framework for that to handle your data requests. HTML+ only handles the templating side of things.