Hi C.,
Honor your instinct and take things slow. I know that CIO seems like a quick-fix, but as a nanny, I saw how it affected the relationship between child and parent, and how the personalities of these little people were altered. I never want to see a child cry like that again and will no longer work for families that employ this practice. Having to adhere to client's CIO preference was heartbreaking for me, and seeing the very real frustration, rage and torment those babies went through made me realize that I could never use this method with my son. Yes, the babies did eventually fall asleep, but as another mother mentioned, there were other problems that arose as these children grew older, not only in how they responded to stressful situations later in life, but most especially in regard to how and where they slept. We can only place children in a crib for so long; eventually, their anxieties can lead them back to your bedroom for a much harder time than one would ever imagine.
Our son has slept with us since day one. He is now 19 months old. If I hadn't had the experiences I had, or the confidence in my mothering that I do have, I might likely have decided he was 'too old' to be in bed with us. We've made some happy adjustments to the love life, and I have to say, I can't imagine our son sleeping anywhere else for now. No matter what he's needing when he wakes up, food or comfort, I can nurse him and he's content. If he's ready to wake, it's far more easy for me to get him back to sleep (and myself) than it would be having to get up, go into a separate room and try to get him back to sleep. Be prepared, if you move him into his own room, it may be an adjustment for everyone's nighttime routine.
For what it's worth, most children do not reliably sleep through the night on their own until they are about three years old. Certainly there are some exceptions to the rule, but there are a lot of young children waking their parents up at night, even if the parents won't admit it.
If you are very certain you need to make this transition, please do it at your son's pace, and respect his need for contact with you. Being alone after nearly 17 months of being connected with you can be a huge adjustment. Lots of love and hugs and a willingness to let him progress at his own rate will help tremendously. Unlike leaving him to cry, reassuring him that you are there and responsive will go farther in helping him have a smoother transition and keep your relationship intact.
It's worth noting, too, that Ferber, the CIO guru, was appalled to discover how widely used CIO was. He never meant it to replace loving parents looking after their children when they were distressed, or as justification for ignoring crying. CIO was developed for only the most extreme sleep problems in families where both the parents and child were not getting any sleep. It was meant to be a last resort for desperate parents who had tried everything else, not the common practice of an entire culture. Far too much is made of "encouraging independence" in young children; at this developmental stage, the child is dependent on their parents being reliably responsive to their needs. Companionship is a very real (not imagined) need for an infant to have, and security is the foundation of a child's successful social and emotional development. Only after the first basic needs are sufficiently met can a child begin to experiment with independence.
My best to you and your family.