With the wisdom of 20/20 hindsight, I'd put it like this... there is no way of knowing whether or how gifted your little one is right now. There are broad ranges for what's normal with very young children and for every gifted child who spoke or walk early, there's one who didn't. For every one who was rational and calm, there's one (like mine) who was difficult and challenging from the beginning.
But that's not the same as discounting the evidence you see as your DS grows. You are the best witness and can use the data you have to stimulate appropriately now and to make choices around testing and advocacy as the years go by.
Again with the benefit of hindsight, I can say that we knew that DD was very smart almost from birth. I can look back at the baby journal I kept for the first year and read the wonder and terror we were feeling around some of the things she did back then. Still, there wasn't much to really do about it at that age... it wasn't like we could keep her from, or alternately prod her into, developing any differently than she did.
Yet, by the time she was struggling through a terrible first grade year, we began to doubt those earlier opinions. Still, those observations are what led us to pay for testing and make changes in her schooling when we needed to.
Also note, DD (now 11) never crawled. She scooted and rolled for a bit and then at 6.5 months she pulled herself up at the couch and started aggressively attempting to walk (and falling down A LOT -- we removed all hard furniture from the living room for 6 weeks until she got the hang of it). It doesn't seem to have hurt her development (intellectually, emotionally, or physically) in any way.
