HalesandPace - Have to disagree with you there. 250 kts below 10,000' is more fuel efficient, especially if ATC bring you below your ideal profile. On the B737 if you set the cost index to zero to get the best possible range, what you get is a 250kt climb and descent. On the DC-9 we used to use a 250kt descent ALL THE WAY for fuel economy - now that really did cause an ATC log jam!