Amazing!
For a free app this is absolutely excellent. Working with blind and VI children this is excellent for me practicing my Braille and for the children to work on and send Braille files. The only draw back I would say is that sometimes holding multiple keys can be quite difficult and you have to press them individually then release at the same time which makes the experience very different from using a Perkins machine for example. It would also be nice if there was a built in zoom function or the ability to change the size of the Braille display so that visually impaired people can use this more easily. But honestly for free? Yes this is 100% worth it.