They all have broad expertise, and their work reflects the sort of eye for detail which is so valuable for this venture. Furthermore, four authors is probably a bare minimum for such a project. DeFirmian did his best with MCO, but it really isn't up to modern expectations. Apparently, the second BCO was done by a team of Russians, but to me, anyway, it also lacks the aforementioned precision. There are a number of other good features to this book.
Every line is given an assessment, a policy which at least guarantees some guidance by the authors.
No big deal, but it would have been nice to see a few others identified, even with no accompanying detail. In other words, the reader is practically guaranteed of an accurate overview of how contemporary theory views a given variation, at least in lines employed by players of master strength and above. Inevitably, I find some problems with this book, although I don't think that they'll impact upon the average player too severely. Let me emphasize that this sounds like a more serious problem than it is. For most players, and for a high percentage of variations, the difference will be negligible.