It ISN"T just their opinion that breastmilk is best for babies, so if they use some strong words to get mothers to breastfeed, and help them succeed, they are only being honest.
A few of these reviews made me laugh. Several reviewers criticized the authors for saying, for example, that you should nurse whenever baby is hungry... resulting in them nursing 24/7 for days on end and not eating or sleeping. Surely, as adults, we can use a little common sense to interpret what we read. Yes, parents are allowed to eat and sleep too, and nature does not intend for babies to nurse 24/7 for weeks. (Though, if the complaining mother had tried a sling, or getting some help from her spouse or friends, she could have eaten while nursing...) If co-sleeping doesn't work in your family, put baby in a crib.
And as for the reviewer who said that the Sears told mothers to avoid treating illnesses so they could nurse ... I suspect she misunderstood. I don't have the book in front of me, but what I THINK they meant was that you don't HAVE to wean to treat most illnesses. The vast majority of medications are perfectly safe to use while nursing, (or have a safe alternative) yet many doctors will tell mothers that they have to wean, at least temporarily, if they are ill and need to take medication. The point is that the risk to the baby from traces of maternal medication in the milk is far, far smaller than the risk to the baby of being fed formula instead. (Even for a short while, and since few mothers are able to pump-and-dump for several weeks and then get baby back on the breast, even 'temporary' weaning very often ends up being permanent weaning.)
And comfort nursing does not teach bad habits...
Yes, the Sears do encourage new mothers to stay home with their babies, if possible. But if the mother can't, she can't, and the book does discuss the issues of employed mothers. (And, to respond to another reviewer, you really CAN get out of the house during the first year while nursing on demand, comfort nursing, and using cloth diapers.)
If you want a book that tells you that "breast is best, but formula is just as good, and if you just don't want to nurse, or you have some minor difficulties and want to quit, that's perfectly ok too," I'd recommend "What to Expect" or any of the other general parenting books. But if you want an honest, well-written text that promotes breastfeeding, doesn't mince words, and helps mothers to succeed, this is an excellent choice.