So, we only did CIO for one night, and it was pretty awful, but we were really going crazy with the sleep situation. I always thought that once you get your kid to sleep through the night, that was it! I mean, sure, there would be the occasional nightmare or request for water, but I was totally clueless about sleep regression and climbing out of the crib and so on.
In our case, Turtle knows how to fall asleep without help, he just didn't want to go to sleep in his room alone. We weren't able to get him to tell us what the problem was, so we couldn't try solving whatever it was that was scaring him or making him not want to go to bed. Staying with him solved that problem, but created a new one: having someone in the room with him was making him too excited to sleep. We even tried putting Tadpole in there in a portable crib - it didn't help at all, and prevented Tadpole from sleeping, too.
Based on a similar situation a friend had with her son one year ago, we decided to put a chair just outside Turtle's room. My husband would get his computer and sit in the chair, show Turtle that he was there working, then close the door most of the way. It worked! And for the moment, it's still working. Turtle has the comfort of knowing someone is there without the distraction of having someone to play with inside his room. Now, we'll just cross our fingers that it keeps working.