I know- I just had to renew mine and 2 kids' in June. I was also worried about the time factor and expedited all three. It definitely costs money- I paid well over a hundred bucks each. I think that when they become a requirement they should cost about 20 bucks- but what do I know?
I live on the Canadian border and it is much easier to flash a passport than to fool around with wrinkled, dirty birth certificates for five kids. Plus I would feel nervous without one. Just MHO. But then again, I do travel internationally at least once a year and my kids have all used theirs as well. Just last year they went on a cruise, one child went to Italy on a school trip and two others went to Panama. Now we have another trip to Panama coming up and my senior just announced they are going to Euro Disney in May.
In the back of my mind I also feel that if there is ever another major terrorist attack I am heading over the bridge to Canada and I don't want a bunch of worn out birth certificates to get in my way!