I just wanted to post my own experience and how our journey has gone, in case it is helpful to anyone.
With my oldest, I had a much more mainstream perspective. I expected to have the baby in a cosleeper until, say 6 months, when she would, of course, be sleeping through the night in her own crib.
Needless to say, I had quite a comeupance. She was in our bed that first night and by 5 months was waking literally every 20 minutes unless I was next to her. Everyone we spoke with said CIO, which we did, and I really regret it. It never really worked. She cried constantly, and I was hysterical, too. She still didn't sleep through the night until after 2 years.
With my second, I decided I would do it all differently. I nursed my DS back to sleep every time. He, too, woke constantly -- every 45 minutes or so. When I was about halfway through my pregnancy with my third, my DH took over putting my DS to sleep and with the nursing to sleep association broken, he started sleeping longer stretches (a couple of hours at a time). We moved him to a bed in a room with his sister around 2 years (he was still welcome in our bed) and then nightweaned him around 27 months. He has slept throught the night fairly consistently since around 2 1/2.
My third child followed the same pattern. I nursed him back to sleep every time and he woke every 45 minutes until I came to bed. We have just started having DH do bedtime and he, too, is sleeping longer stretches.
I guess this is a short way of saying that based on my family I do think that Ferber is right: kids who are nursed to sleep may have a hard time resettling themselves if the nipple isn't there when they wake (I say "may" because I know plenty of kids nursed back to sleep who can resettled at least a couple of times before needing to nurse again.).
For me, the next question is, is a nursing to sleep association a problem. In a biological sense, I don't believe it is (I highly second the recommendation to read "Our Babies, Ourselves" by Meredith Small.) I think this is the way babies have evolved to behave for a reason and I think that if we can accept it, they will either grow out of it or be able to more easily accept an alternate method of falling asleep eventually.
The other challenge is meeting the sleep needs of the other members of the household. I have done this by going to sleep very early (usually after DS's first waking). That means my evening time alone has been just 45 minutes, which sort of sucks, but I also know this stage of life is fleeting and I believe that meeting my children's needs is crucial. I also believe that you can change sleep associations much more easily at, say 1 1/2 or 2 years, if constantly nursing back to sleep doesn't work for your family.
Good luck to everyone who struggles with sleeping. It's a hard road, but I promise that they do sleep eventually!