I haven't always been a fan of online learning--for many years, I liked the face-to-face best, especially when it came to feedback on my writing. But in the past ten years I've grown very fond of online classes and how they actually enhance writers' ability to give and receive feedback. I regularly take them for motivation, accountability, and the helpful responses I get for my work-in-progress.
I think there's a great use for them, in the journey of a book, and that's often in the generative and early revision stages. I don't find as much help when I'm closer to final revision, because seeing only parts of a manuscript is less helpful then.