The ever-helpful Review of Biblical Literature has published Raymond Collins' review of Witherington's book:
Ben Witherington III
Letters and Homilies for Hellenized Christians: Volume 1: A Socio-Rhetorical Commentary on Titus, 1-2 Timothy and 1-3 John (Amazon.com)
http://www.bookreviews.org/bookdetail.asp?TitleId=5714
Reviewed by Raymond F. Collins
Collins is generally accepting of Witherington's work despite their disagreement on authorship.
I've read the introductions and various other portions of Witherington's section on the Pastoral Epistles and can recommend it.
Posted by Rick Brannan