[DISCUSS] What Dan Sullivan Course/Training?

So I've been through many training courses here on FUB and I keep hearing Dan Sullivan's name come up.
Guys such as Joe Polish, Brendon Burchard, Fran Kern and Eban Pagan talk about him throughout their
trainings.

I figure if these guys talk about him this much he must be worth studying, right?

So have any of you guys been through his trainings? if so is he worth studying?

What courses/training of his would you recommend?

Thanks in advance.