I ended up splitting a full ($180) membership with a buddy, partially for Franklin's course and partially for a few others, and I can say that it's a solid course. I've read his "Manifesto" book and it's similar enough to where I don't think you miss much if you just stick with the book, though. If you're also interested in, say Penn and Teller or Annie Liebovitz's photography, or Neil Gaiman stories then Masterclass is worth it.
Having taken the course, I better understand how brisket renders, how to approach a fire, and how important it is to actually have a cook day plan and take notes along the way. If you're new/intermediate it'll help you; if you're old hand you might pick up a few things but there's no secrets he's letting you in on.
The only real criticism I have of the course is that his way of building and maintaining fires is really geared toward his smokers: a round firebox with no fire grill/grate on it (the fire is directly on the bottom of the firebox), no baffles, and a few inches of barrier around the door. I'm cooking on a square box Klose and his fire management method just isn't right for my pit.
