On a strictly personal level, this may be the most depressing thing I've read in a long time:
The Hardest Game. For Adults.
I don't really miss being a kid. I like the adult I grew up to be (and, quite possibly, am still growing up to be). But there are things that I miss, and being able to just sit down and lose myself in a world of my own creation is one of them. I don't know how much of that is neurological, and how much is lack of unstructured time (and energy), and how much is lack of practice, but I miss it.