I sent my son to child care at 20 months, not for his benefit, but for mine as I was a single parent with little support and needed a break. We do attachment parenting in our family so this was a big deal for me, but in the end I think it was unavoidable.
Initially it was great for him, he loved the adults and his interactions with the other toddlers were mostly positive, despite most of theme not being at the same verbal level he was at. He didn't sleep at all in his first centre (7months)and instead chatted away to the carers at nap time and enjoyed being the centre of attention (normal!). I was happy with this arrangement, as I knew he'd be very distressed if they pressured him to sleep without me.
As he got older (and moved to a better centre) he really enjoyed his time there and began to play with the other children, however he found it very frustrating trying to relate to children who were more impulsive than he, and his strong sense of justice really came out then. His expectations of other children were very high. He understood that pushing another child over was not an acceptable way to respond to conflict, and according to him, the other children should too! Tricky stuff for a 3 year old to cope with.(Frustratingly, he's now exploring aggression fully at 6, sigh.)
I could say a lot more about his experiences with early childhood education and how it led to my choice to homeschool but I don't think that it would be relevant to the OP.
