Betz exhibits a massive control of the literature on Galatians and especially of the ancient literatuer relevant for understanding it. He has a gently rigorous way of demolishing fanciful and unsupported exegesis of the past while still taking clear positions on controversial issues.
Hans Dieter Betz is a German/American scholar of the New Testament and Early Christianity at the University of Chicago. He has made influential contributions to research on Paul's Letter to the Galatians, the Sermon on the Mount and the Greco-Roman context of Early Christianity.
A very thorough commentary. It is true that "Betz exhibits a massive control of the literature on Galatians." However, I won't follow him on many of his conclusions.