Agreed with LD1, those articles/links/videos are talking about smooth traffic flow and nothing else. They don't apply to me or my driving style, which is "driving for optimum efficiency and longevity of my vehicle". I don't care what the other idiots on the road do. I'm out to make the drive as easy on me, my vehicle, and my pocket as possible. I live in an area where there is VERY little flat ground. Everything is inclines or declines. Even the tops and bottoms aren't totally flat as they generally slope to one side or the other as you turn to go up or down the other side... Cruise control wastes fuel in areas such as mine. There is no need to throttle the heck out of a vehicle all in the name of "maintaining your speed". There are many vehicles sold BRAND NEW that cannot maintain the posted speed limits on my local hills at wide open throttle. If you did that twice a day, five days a week, you would blow your car up.
I lose a little speed going uphill to conserve fuel, then make the speed back for free going downhill. My average speed actually varies day to day and moment by moment. If I'm fighting a headwind, my average is lower than when sailing with a tailwind. This is called the "Rolls-Can'ardly Driving Method" and is the most efficient way to drive any car. The vehicle will last longer, and your fuel economy will show a vast improvement. (Rolls-Can'ardly technically means "Rolls down the hill. Can 'ardly make it up the next." - Yes, it's a hillbilly thing...)
*EDIT* Vehicle longevity is important to me. I just purchased a brand new truck on the 28th of March. I have over 22,000 miles on it so far.