In the adoption class we took when we started this process, we learned that a common reaction of kids when they meet their parents is to reject one or the other. We also learned that grieving was normal. Surprisingly - to me, at least - is that both reactions are considered healthy and actually good for the child. They indicate that the child has bonded to a caregiver and is grieving that loss.
For Quinn, the grieving process was retreating into himself and crying all night in his sleep his second night with us. He needed a good week to warm up to us. For the first couple days, he refused to make eye contact and was so deep into himself that we were convinced he was autistic.
Two other couples we met yesterday saw very different reactions.
One couple, experienced parents of special needs kids who adopted a 2-year-old, found that their new daughter completely rejected the heartbroken mom. It's been a week now and the little girl will look at her mom, which is progress, but will not let her hold her or feed her. I had heard that a good thing to do in cases like this is for the preferred parent to hold the baby while the rejected parent feeds her. Not sure if that works, but maybe it's worth a try.
Another couple adopted a 2-year-old girl who was deeply attached to her foster parents. Hand-off was very difficult; the entire foster family, including grandparents and aunts and uncles, showed up and sobbed. The poor little girl was despondent for an entire week. She smiled for the first time on day eight and is showing small signs of progress.
As we prepare to head home, I do not pretend to be anything close to an expert on this whole process. All I can say is that, from what I've seen, children respond and bond and attach in very, very different ways. It seems like the best thing to do is learn about what might happen so you're prepared, but not worry if it does happen. Almost every problem experienced by the people I've met here has either disappeared a few days later or is waning.
My other advice would be to avoid comparing your kid to others. That's not easy when a 13-month-old in the playroom is obviously considerably more advanced than your 17-month-old, as we saw this morning. But every kid is on his own schedule, handling major, major upheaval in his or her own way. It's amazing, really, considering all they've been through, that they're doing as well as are.