Yes, it's interesting. Meanwhile, my DS was mildly advanced at age 2 but nowhere near DD in his capacity to make you go "Whoa." For a while I worried about having one very gifted child and one child who was bright, but likely not gifted. Fast forward to DS learning chess at 3 and reading chapter books at 4. One area where he is still far behind DD at the same age is drawing and writing, but DD is notably gifted in these. (Although....her drawing ability was relatively more impressive at 4 than it is now. She still has an incredible artistic sensibility and skills, but at 4 she was sort of jaw-dropping.)
It's possible that DD is as gifted as she once appeared but that this is being obscured by other issues (she is dxed with anxiety and depression and may yet receive a dx of ADHD, ODD, or ASD). Her daily emotional struggles take up a lot of time and energy these days. However, she was a very challenging toddler as well.
Another interesting thing about DD is that she has synesthesia (
http://en.wikipedia.org/wiki/Synesthesia), which we did not discover till she was 6. I believe her brain is very unusually wired in a lot of ways. Much of her early precocity was memory-based, and she does continue to have an incredible memory, but that takes you only so far (doesn't allow you to understand advanced math, for instance). It certainly helps in school, though. (Memorizing math facts is effortless, for instance.)