Both my kids walked early: 8-9 months. They crawled--they didn't skip that developmental step--but they didn't crawl for more than 2 or 3 months, maybe ages 3-6 mos. They "cruised" (walking by holding on to furniture or people) for a couple of months, and then they walked. It all seemed really fast to me.
DS4 was a climber, but DS7 wasn't. Honestly, I think he was too sensible to risk his neck that way. He definitely had the physical capability, but he was much more aware of the dangers than most kids older than he would have been. DS4 is a bit of a daredevil, so he didn't care about the risks. DH often tells him when he does something risky that hurts him: "If you're going to be dumb, you have to be tough." It actually seems to have helped cut down on the incidents of risky behavior, believe it or not.
(Not *my* parenting style, but if it works...)
On a related note: both kids held their heads up pretty much from birth. The nurses and my parents noticed it with both kids. DS7 was exhausted from the tortured of our induced labor and delivery, and he slept for a day. But once he woke up, he held his big ol' head up in a wobbly fashion. It was kind of freaky. He didn't always have good control, and he often very nearly dislocated my jaw with his battering ram head! DS4 had better control. (Or maybe I was more accustomed to avoiding the accidental assaults? Not sure...it does seem like he had better control.) DS4 has always seemed more physically advanced by a narrow margin and DS7 always seemed more intellectually advanced by a sizeable margin.
IMHO, I think physical precocity can indicate GTness if it is part of a general state of advanced behaviors. I don't think we can isolate one behavior--like climbing--and say that it indicates GTness. But if lots of stuff happens earlier than normal, it's probably a sign that something's going on.
