The other way that one could go through traing in child psychiatry is through a triple board program, where you get board certified in peds, general psych, and child psych (in 5 years, the same amount of time it takes to do general psych and a child fellowship). It is pretty hardcore and it definitely for those who want a more medical edge to their psychiatry practice, ie consult-liason.
I am starting my psych internship this summer and am planning on going into child eventually. I did two months of rotations in inpatient child psych, and that is what made up my mind. You definitely have to find an attending who likes to teach to work with - I think that makes a big difference. I love kids, but even child psych is different than I originally thought it would be. These are some really troubled kids - but it is definitely worth it.