I tried CIO when my DS was 11 months old. He was a good sleeper from 4 months on but when he reached 10 months-just started to crawl-his sleep habit became pretty bad. He woke up 2-3 times at night and some nights he wanted stay up and play for 2 hours(like 3am...)
He refused to take naps and it took me hours and hours of rocking to get him to sleep for 30 minutes or so...
I finally decided to do CIO for naps and bedtime and he cried for 1 hour and 30 minutes first night. Some naps were all crying. It was getting better..Some night 5 minutes then fall asleep..He didn't wake up during the night anymore. Or he did, he cried a little and went right back to sleep. I knew I could not stand any longer and seeing my baby all tired crancky during the day was worse.
I did it for 2 weeks and I stopped since I got such a negative support from my DH and my live-in MIL. Although my MIL was convinced towards the end that she even let him cry to sleep one night when we were out.
He's 14 months old now and I soothe him to sleep for naps but at night I do bedtime routine then put him in his crib, he rolls around and talks to himself for 30 minutes or so then falls asleep on his own. Even for the naps, sometimes I rock him for a while then put him in his crib, he sleeps. He has pretty good sleep pattern(or getting better) and he sleeps good 10-11 hours at night without waking up.(even with my DH's snoring!)
Only thing I have to pretend that I am there next to him... Due to renovation and flood in his room, he's with us. His crib is right next to our bed and it worked out fine.
Time to time he fights to go to bed or wakes up...I let him cry to sleep sometimes or pick him up to soothe him. All depends on intensity of his crying.
CIO was really hard for me too. I thought I was dying watching him through the monitor but I knew I was doing the right thing for DS. But when all pissed off DH yells at you while he watches him with me. I gave up becuase it was harder for me to argue with DH ALL THE TIME.
Good luck and hope it works out for you and your baby.