Earlier quoted context omitted.
I usually sign up for a bunch of classes just so I can access the material at a later point when I have time or when I'm interested. How many of those classes have you done the work for? Personally I find the synchronous model helps me complete the course, as it removes the temptation to put things off.
I think the synchronous model makes it easier to have small communities of students working through the same thing at the same time, helping each other.
I also find the assignments/exercises on the courses are first class and that's where a lot of the learning comes in especially when backed up by discussion forum activity from other students. Watching the videos on their own doesn't really appeal to me.