I have a nearly one year old so this is a "hot" (i.e., much discussed) topic in our house. Fortunately my husband and I are in agreement regarding CIO. As parents our job is to comfort and teach. We have taken turns comforting our little one and only within the last two weeks have we even attempted CIO when nothing else was working. We hate doing it but when no amount of comforting helps, what else is there to do? Our little one settles on his own within a few minutes (7 minutes max) so the torture doesn't last long. We did not try this at an earlier age as it went against our grain as parents despite everyone telling us to go that route. When we felt like he was fussing but not crying out of a overlooked need, then we started talking about and then trying CIO. Determining that difference in cries is the point of when to try CIO I believe.
We discussed our rules of CIO after researching the topic and then we tried our version of it (5-10-15 with picking up to soothe). The first few times one of us would chicken out but that was okay. We just stopped trying but one night we were committed and it worked. We felt bad but we just supported each other. The next night we had to do it again but it was a much shorter duration. In all it lasted three nights and our little one has gotten better at settling himself. It’s one of those crummier things you do as a parent since no one wants to hear their child cry.
When we came home from the hospital a friend of ours forwarded us that 'Mad About You' episode regarding this very topic. No way were we going to sit there in the hall and do what they did. While it was really funny, it was also gut wrenching. However, we both understand to each parent their own styles/decisions. What works for our family does not necessarily work for another. We can and do go without sleep because neither of us can stand listening to our baby cry. It's just part of having a baby in our minds. This stage won’t last long so we just support each other and take turns.
As for when to try CIO, I would certainly not try it before six months. It would just be cruel to listen to a newborn or small infant cry for very long.