I don't care how many kids I have, I can never stop being excited when a baby reaches a milestone. It holds the same excitement that watching my first learn to roll over, sit, crawl, talk and walk did. I think maybe it actually gets worse when you have had several kids. I notice every little development. "Hey hes vocalizing 8 different sounds now! Last week it was 4!"
For instance, my baby can grab his feet, and suck on his toes.