For my own part, I generally like the Etz Hayim, despite its many shortcomings. One must bear in mind that it is not meant to be a mission statement for the Conservative movement, a theological treatise, or a guidebook for living a halakhic life. As a synagogue chumash, its purpose to help laypeople understand the biblical text and to introduce them to modern biblical scholarship, traditional Jewish exegesis, and some of the connections between the Torah and modern Jewish life. On those terms, I think that the commentary is largely successful.
Rossman-Benjamin's major criticism of the Etz Hayim -- and, by extension, the Conservative movement -- is that it presents the Torah as a human, rather than divine, creation while still insisting that Jews accept its authority. Her criticism is reasonable insofar as simultaneous acceptance of historical criticism and rabbinic halakhah leads to practical and theoretical problems that have yet to be satisfactorily resolved by the movement's leading thinkers. However, the strict dichotomy between "human" and "divine" is false. In my opinion, failing to acknowledge the possibility of a middle ground between these two perspectives on the Torah's origin presents a greater threat to the future of Judasim than openness to the conclusions of modern scholarship.
This article by Rabbi Gordan Tucker puts it nicely:
[I]magine that you are picking up a new book, one, say, with no title on the cover, so that you begin to learn about the book only upon opening it. You first read a preface. It says the following: "The volume before you is the result of relentless investigative reporting, and though its claims may at times seem incredible, they are all thoroughly documented." So you read on, and are fascinated, perhaps even shocked, to learn facts that you never knew. It changes your life and the way in which you look at things, and you eagerly pass it on to others so that they may know these facts as well. Then one day you discover that the book that so profoundly moved you was actually quite shoddy and was based on very fallible sources. Some of it was even just made up. How do you feel? You feel betrayed. The author has made a fool of you. He claimed that the work was factual, you let it affect you accordingly, and you were duped.
Now on another occasion, you might open a book and find a preface that says, "What follows is a parable.” Or better, "This is a work of fiction, although it is based on fact." You now have a different orientation to what you are about to read. You read it, and you find it to be one of the most moving and true books you have ever read. It also changes the way in which you look at the world, yourself, and your place in it. You live somewhat differently because of it. Now someone comes up to you and says, "You know, what [the author] said in that book didn't really happen, certainly not the way in which he describes." How do you feel now? Would you not say to this person, "I never assumed that it was all perfect fact. And the book's power to change my life had nothing to do with a perfect historical fit."
Consider this:The first two chapters of Genesis tell different tales of creation. If we accept that we have an edited compilation of different narratives, does that mean we must believe that the world had no Creator? Or does it not rather mean that what we have in the Torah are different versions of the same belief that we are God's creatures, but told in different ways, with different emphases, including very different understandings of the role of women in the world, produced by believers in different places and different times?
Some Jews take God as the sole and final religious authority. Some Jews take the thinking autonomous self as the sole and final religious authority. It is the particular characteristic of Conservative Judaism to insist that religious authority is a partnership, that it comes from the reality of a revealing God and the equally inescapable reality of a seeking, evolving community through which God's words get expressed over time.
*There are a few inaccuracies, which I noted in a comment on DH's post.