My impression, which is purely subjective, is that the OT is a major stumbling block for people (and a major target for attack). While the NT also has problems, I feel there's a qualitative difference. For Paul to say "wives be obedient" isn't wonderful, but it isn't in the same league with a story where an unnamed concubine is gang-raped and then cut up into pieces, so she can serve as an object lesson: to me, those are different levels of "bad."
It's fair to say that I am a minimalist, and if it were totally up to me, I'd go with a Thomas Jefferson approach, so that the Bible would consist of the Two Commandments, the Golden Rule, the story of the Good Samaritan, the story of the Talents, the Sermon on the Mount, and perhaps a few other bits. I guess this would be closer to a Buddhist version of Christianity, where people sort of "meditate" on the Two Commandments.
That's just me, and I don't have any desire to promote that as a good solution in general. The OT, on the other hand, contains enough overt violence, intolerance, and bigotry that I do feel Christians should formally and publically renounce it. I think that's the right thing to do.
(Thanks for taking a look at the book!)