I purchased the Summa for reference, having an interest in Theology. I consider myself an amateur Theologian the subject is to important to leave to the professionals! However I found the introdution absorbing and have read large portions of the book. Considering the time the Summa was written, that the book is abridged and translated I found it very readable. In particular the first section on God shows great insight and is still relavent to the modern mind, St Thomas teaches we can know God but not comprehend him. Being a Christian I found the book useful and deserves a place on any bookshelf.
For those of us who do not have the time to physically sit down and read all five books of the Summa, this is most certainly the closest you will come to consuming the real thing! I found this after I had began to read the first few chapters and nothing comes so close to capturing the essence of Aquinas's writings so thouroughly (and in only a sixth of the size of the original)! This book is a must for the true Thomistic scholar!
I struggled with accessing Aquinas for my dissertation. I found McDermott's publication very accessible and very useful indeed. I owe McDermott a debt of gratitude! Even though it is a sizeable book, it is not cumbersome and it is portable. It is well written and for me, is the best translation of Aquinas' Summa Theologiae.