I ordered his commentaries (Witherington) on Acts and Corinthians several years ago hoping there was some fresh perspectives of Greco-Roman culture. Basically what he tries to do is look at everything through a lens of Greek forms of rhetoric, showing how various arguments are not just imperical formulas under western ideas of induction and deduction, but rather in line with classical modes of pursuasion found among the Greeks and Romans.
Although this seems promising I have to say I can barely read more than five pages without feeling like a great backslide has occured even compared to Calvin's commentary on Acts. The insight is sadly lacking and the commentaries are not thourough verse by verse explanations but just platforms to propose a few average ideas with an attempt to show support for them by a section of scripture. What I mean is, he proposes some cultural idea to explain a key verse, which is often already moticed of in many old commentaries, then he half hazardly tosses a few more verses in the subseqent paragraphs to support his premise. In the meantime he almost ignores all the real meaty subjects that a true verse by verse commentary would typically cover.
In the end I would say it is all much ado about nothing. It is a fresh idea about sheding new light in a commentary that plays out to have little value in actually breaking new ground. I think he would have done better studying Jewish culture and looked at it through that lens, but that was probably not his major.