What can you learn from the Navajo course? Is it worth it?
Some vocabulary and very preliminary grammar. Very much an introduction to the language. There are quite a bit of errors, so reference to outside resources like Wiktionary and Navajo WOTD are really pretty crucial to learn things correctly. Considering it's free and not that long, I would say try it at least, but keep in mind that the course is very much in an beta (almost more like alpha) state and is in need of quite a lot of polish.