We did Crying it out with our now 2 year old, at 7 months. It was hard for the first 2 nights.
At that time, before I decided to go for it, she was still waking 3-5 times a night and wanting to nurse for comfort. We were also rocking her till she was asleep and then having to very gently lay her in her crib and sneak out - if she woke, we would have to start all over again. She was also a horrible napper - after rocking to sleep and laying her down, I was lucky if she napped for 20 minutes at a time, maybe 2-3 times a day!
I read the book "Healthy Sleep Habits, Happy Child" - it really helped me understand what she needed as far as sleep. We decided to let her Cry It Out for my sanity and health, I was not getting much sleep at all.
The first night, she cried/screamed for 45 minutes....then she fell alseep, and slept from 7 pm to 12:30 am, nursed once, and went back to sleep without crying, from then till 6:30 am - it was like HEAVEN, and that was just the first night. That success gave me the strength to keep going. The second night she only cried like 20 minutes, and then slept till 12:30, nursed and slept again till 6:30 am!!! Third night the crying was about 10 minutes, and the 4th, maybe one little whine as I left the room! Ever since she has beena great sleeper at bedtime and nap time....with a few setbacks at holidays or when sick or teething, but nothing major.
SHe actually asks to take a nap or go to bed when she is tired, and always puts herself to sleep happily.
Also, check out her room - from as early as 3 months, CJ wouldn't nap in her bedroom - we figured out it was too bright in there, once we hung light-blocking curtains, added a cd player of lullabies on repeat and a small circular fan on the floor, she did SOOOOO much better. We also make sure there are some stuffed animals and board books in her bed with her for her to look at/play with as she is falling asleep, and after she wakes up. She will play happily in her crib (has since we did CIO) for 1/2 to 1 hour after waking in the morning!!!
Good Luck!
Jessie