Could this really be classified as a cult? I read the entry, but it seemed to me that it was more of a doctrine that some Christians adhere to. I didn't see where it said anything about "Quiverfull" being the religion. It looks to me like a small part of of some people's Christian beliefs, if that makes sense.
As far as what I think about the movement itself, I think it has some good points, and some bad. I have read a lot about birth control pills possibly being "abortifacients" meaning they encourage early abortions by making the uterus a hostile environment that the newly formed embryo/blastocyst cannot implant into. Since I believe the moment of conception, and not the moment of implantation, is the beginning of human life, I stopped taking the pills. But we do use other non-hormonal contraception.
I can see the other side, the whole "just trust God to give you as many as you can handle." But then on the other hand, I know that God gives us a brain, and He expects us to use it. In every area of life, we Christians make decisions based on using our noodle. I don't see how planning your family is any different.