To my knowledge, his free-will book was not taken seriously. Harris seems to come to several reasonable conclusions, but he defended them very poorly. There is nothing wrong with being an incompatibilist, however, his book was not very sophisticated. This and this are some interesting places to here some of Harris' perceived not-so-great points. I can't think of any of the top of my head, but even those who agree with Harris' conclusions do not put forth arguments he attempts to articulate, as they see them as not-so-great.

In my opinion, Dawkins is much, much better. His books "The Selfish Gene", "Ancestor's Tale", and "Climbing Mount Improbable' are all great books. However, that is about where he ends. As soon as he starts talking about theology or philosophy, he is out-of-his element. Harris, on the other hand, has not produced any worth wile professional work (The Moral Landscape, Free Will, and The End of Faith, at least in my opinion, were disasters) and his private persona (that of a podcaster, public intellectual), is even worse considering his thoughts on the Middle East, Islam, as well as pretty much any other topic he has weighed in on. And it is not getting better, as far as I can tell, as his recent stunts and mishaps with Jordan Peterson and Charles Murray have demonstrated.