Every time one of my children (and, naturally, their age-mates) approaches a milestone, I notice hints of panic among my parenting peers. One of my coworkers (her children are all grown, I think her youngest is 14), in her well-meaning way, asks after my kids and their development, a hint of that same worry edging her words. "Oh, L isn't walking yet?" "J still has trouble with those words?" "What do you mean he doesn't ride a bike or scooter?"
My approach to parenting, overall, is to wait and see what happens. I have friends whose children have been in speech and/or physical therapy to address developmental issues, but by and large, kids do things when they are ready. I'm not saying that some kids don't need intervention, I'm just saying that the sense of panic I detect in so many parents may push kids who don't need intervention into it. J walked at 15 months. He would not go up and down stairs until about 2 1/2, and then he broke his leg and went back to square one on that front. He didn't start jumping until he was over 3. He's the most physically cautious child I've ever known (other than the occasional "jumping on the couch when he's not supposed to" thing), but he's doing just fine. He started talking up a storm right at age 1, and has been ahead for all of his cognitive milestones. Now, at age 4 1/2, he is a normal (and smart and weird) kid. He can pronounce our last name perfectly (all 4 Polish syllables!) and his imagination knows no bounds. He can also pronounce Quetzalcoatlus, which is a damn impressive accomplishment, but the letter J poses a problem. Said alone, it's somewhere between J and "Shay" and his name comes out as "Dames," but he can say "Jim" with no issues. I asked his pediatrician over a year ago whether or not I should have him evaluated (he still has problems with double-consonant sounds, like "slide", where he only pronounces one of the sounds, like "lide"). She is pretty laid back about things (and we LOVE HER, which is why we still go to her, even though she's not covered by our current insurance), and she gave me the information for a local therapist but said she didn't think he needed an evaluation unless I wanted to get one just for my peace of mind. C's family (and one of my brothers) has a history of speech problems early on, but as I've watched J grow, I've watched his speech change as well. He slowly but surely perfects words. Yes, his speech takes a moment to adjust, but I'm not worried. I never called the therapist for an evaluation for him.
With L? Well, that child is also a chatterbox. Her verbal stuff has slowed (and backtracked a wee bit) since she's started trying to walk, but that's pretty standard. She avoids walking unassisted at all costs (beyond 1 step) but will cruise from item to item without batting an eye. She crawls like mad, but did not crawl until she was 11 1/2 months old. She has been trying to stand up since birth, and will now stand in the middle of the floor, then carefully drop down and crawl rather than try to walk. Yesterday she spent 10 minutes positioning a walking-pushing toy to just the right spot so she could cruise from the kitchen all the way across the living room without having to let go and walk alone. If she's not walking at 15 months, I won't bat an eye (but if she makes it to 18 months and still refuses, I'll be shocked). She'll walk when she's ready.
As someone on my April 2011 moms group put it, when baby is 30, it won't matter that he or she didn't walk/talk/whatever at 15 months. Time is the great equalizer in all things, and this is no exception.