Like his magisterial Anchor Bible commentaries on Romans, Luke, ans the Acts of the Apostles, Fitzmyer's commentary on the Letter to Philemon represents the finest of modern biblical scholarship.
The commentary was quite interesting, and Fitzmyer is definitely a brilliant theologian. His extensive knowledge of Latin and Greek enhanced the series, introducing parallel ideas from a wide range of sources, including Church Fathers, Latin historians, and many more. Even though the notes of it felt more like a Greek lecture than anything else, and if you don't study the letter with the Greek text nearby, it might be hard to follow all the grammatical details he points to, often becoming frustrating, it was still an amazing resource to read.
I did enjoy this commentary. For readers who are unaware, Fitzmyer is a Roman Catholic but I did not find his tradition really coming out (for instance, his interaction of the word "saints" in Philemon is interpreted to refer to believers in general, not SAINTS, and he did not have any further discussion about that point of saints and SAINTS). In the past I have used various commentaries from this series and I think this volume is one of the better ones (there are some whacky ones in this series). I read this work primarily for my exegetical preparation for preaching, so in terms of it's usefulness for the exegete I thought that this work was worthwhile in terms of the materials for the readers to interact with, though I feel that there was more that Fitzmyer could have said. By saying that this work is worthwhile, I do not mean that I agree with every interpretative decision made by the author, only that they were not outrageous or out of bounds where he landed. From time to time there were historical, lexical, grammatical and syntactical insights that I gained about the Greek text from reading Fitzmyer, that I didn't not see on my own.