It's the pre-milestone moments that are the most amazing. The milestone moments themselves are quite bittersweet, as you know your child can finally do something is amazing, but the build up over the previous weeks and months is no longer there. All that work - trial and error that went into the activity is now over, and all you're left with is your child being able to do something they couldn't do before.
I guess this is just natural, or else my mum and dad would call me up every day and a) be amazed I can talk and b) be amazed I didn't kill myself with them not around to look after me.
As I write this, I am currently committing to memory the last few pre-walking milestone days we have left with Emily. She's able to take a couple of steps by herself and then either teeters over or collapses. It's been a lot of work for Sue and I, as well as a lot of work for Emily, constantly being told, "c'mon Em, you can do it", like you'd say to a pet dog or trained chimp.
After this milestone, I don't really know what's next - talking? brushing her teeth by herself? eating WITH chewing?
It's a lot of fun seeing development through a child's eyes and long may it continue.