My dd is 3 and we never let her CIO. But a good friend who had her baby 10 days before I did ferberized her son when he was 6 months old. I found it heartbreaking, and so did she. She would call me for support while he was screaming and it was really hard to be loving toward her at those times.... but I was, and I'll tell you why.
My friend was raised in a strict household. She is a very orderly person. She was really struggling with motherhood. Her marriage was suffering; she was depressed. Occasionally she would feel rage at her son -- I mean real true rage. My friend is highly intelligent, educated, and she made a decision about what she needed to do to survive parenting her son. I do not agree with her choice -- I *strongly* disagree, in fact. Her son really suffered -- I heard it. But my friend was suffering too, and she was the one living in that house with her boy and her husband, and her history. She did what she needed to do. And I love her dearly and she is still my friend, although I confess that at the time I did not know if we would stay friends.
So I agree with what someone above wrote when she said that we cannot judge. I do feel CIO is waaaaay too mainstream -- scary in fact. But there are situations where people do it and maybe that is what they needed to do.
IMHO CIO is the antithesis of attachment parenting because it constitutes an intentional fracture of the child-parent bond. Letting a child CIO teaches him/ her that they are alone at night -- that there is no point in crying because they will not get your attention that way. I am talking about real Ferber here -- returning every few minutes to a fussing or complaining baby is not CIO, I don't think. CIO is leave, return after 5 minutes, then 10, then 15, then 20 etc until baby sleeps. The next night start at 10 min, then 20, then 30 etc... No matter what, you do not go in.
To me, attending to my dd was/ is about respecting her as a whole person, and equal member of our household. Sure, my night time attention to her has changed as she had gotten older. Some nights now I read to her, cuddle her and then leave. Often she asks meto stay, but sometimes I gently explain why I can't stay tonight, but that I will come up in 10 minutes and check her. Most nights I lie with her until she falls asleep and then I leave.
The car seat problem is interesting, but I have to say that we did not go around with our dd much when she was small because sje did not like the car seat. Why should I force her to sit there when she does not like it? But then we live downtown in walking distance of everything we need and I gather from reading these posts that many people do not live in that setting and di not have the option of just walking instead of driving on your errands.