My DS9 was also one of those very, very alert babies.. watching people the day after he was born, and raising his head up to look around. I got told off by a nurse for not "supporting his head"! I was like - what am I supposed to to? Restrain him from moving it? lol. He wasn't particularly advanced in any other physical regard.. sat at 5 months, walked at 11 months.. right within normal range. He did start talking a little early and then his vocabulary absolutely exploded around 1 year. By the time he was 18 months I had to stop counting the words he knew, because it had gotten up over 250 and seemed silly.

~amy