For those of you that have been looking for a good way to learn PowerApps and Flow, especially if you were using InfoPath and Designer Workflows or NINTEX, I highly recommend the EdX course
Developing Business Applications with PowerApps and Microsoft Flow
If you want to get a certificate at the end of the course, it will cost you $100.00, otherwise it is free.
It is a well thought out course and the assignments are excellent. The assignments are actually up-to-date and the features they ask you to use are all available on the PowerApps and Flow sites.