Doing a brief search online I came up with some interesting things from which you can form your own opinion (it didn't take long for me to form mine!

):
John Ortberg: Educated at Fuller Theological Seminary (M.Div and a Ph.D. in Clinical Psychology), where he is also on the Board of Trustees. He pastors a "Willow Creek" church in Menlo, CA. He has written a plethora of books of which I would have you take notice of the titles and the reviews provided of them online. And lastly, I found this page that has some "interesting" information,
John Ortberg Promotes Contemplative Prayer.
Dallas Willard: Professor of Philosophy
B.A., Tennessee Temple College (Psychology), 1956
B.A., Baylor University (Philosophy & Religion), 1957
Ph.D., University of Wisconsin, 1964
Specializations:
Metaphysics, Contemporary European Philosophy, Theory of Knowledge, Ethics, History of Ethics, the philosophy of Edmund Husserl.
Again, see this site for some criticisms:
Dallas Willard — Promoting Contemplative Prayer and Mysticism.