I'll give my pennies worth although I'd not done other online classes to compare it with.
I really like that you can watch several samples before enrolling so you get an idea of the level, teacher's style and the content. Being able to interact with the teacher was good but I only really did that with the stupendous stitching one (new materials for me) and got quick answers. Having samples of other students work to look at really triggered ideas. I like that you can take notes and it marks where you made the comment.
I found the general ones disappointing, but there again they were free so I can't complain. Taking the first class last December really triggered my love of fabric and quilting again after a bit of the doldrums and with that and joining the forum I've not looked back.
Wait for the special offers and it's a lot cheaper. Go for it
What an idiot, I've done several classes on here now