Yes that course is totally worth it, it took me a week to complete it. Before taking that course, I relied on Bootstrap, and didn’t really know how to lay things out and make pages responsive. But after the course I came out with so much knowledge about CSS, not just basic CSS but advanced concepts as well.
I can say that it really stepped up my game, I even went back and redid my portfolio, and it really shows, not only do you come out with CSS knowledge, but it helped me with my design skills, as Jonas lay out his projects in a modern and beautiful look, and for spending that much time doing the course, you tend to pick up some ideas / concepts for your own designs.