I agree with the majority of it. However, the first part about slowing down, there are parts that are subjective and will vary depending on your vehicle. The author is basing most of the conversation on his truck and trucks in general. So most of his points are valid, to a point. An off-road magazine did a MPG test a while ago, and actually found that going really easy on the gas from a stop can use MORE gas than moderately accelerating and getting into your cruising gear as quickly as possible. Of course, do your own tests with your own vehicle as your results may vary. His general claim of 25% throttle is best is not going to be true for everyone. That's about how I happen to be used to driving my truck... I get 10 mpg.
I have found cars to vary a pretty fair amount in this arena. You would think slowing down would benefit cars also. However, my DD is a 99 Lumina. I drive backroads to work, 16 miles one way. When I first started I deliberately went through a couple of tanks of gas at the speed limit, 55 mph most places. My car returned 24 mpg. Not terrible. But then I did a couple of tanks not worrying about it, so there was a good amount of 60-65 mph going on. My car returned 25.5 mpg!
My friend Zach has a Grand Marquis. He gets better mileage at 80-85 than 70 on the highway. In both of these cases, Zach and I believe that gearing is the major factor. Both cars have high (numerically lower) gearing that actually lugs the engine at low rpm's. Raise the rpm's and you put the engine into it's main torque band, which is where your engine is most efficiently using everything.
Tuning your engine helps a lot too. Yes it's "expensive", but get an O2 sensor and tune with it. It may be the best $300 you ever spend. Which by the way, is cheaper than that intake/carb combo you want to throw on your truck. Actually using the correct parts will also help. Don't put on a 3" dual exhaust and expect to gain mileage. Your truck may sound cool, but it probably is not at it's most efficient. Most times a 2" or 2.25" dual exhaust will actually be best.
Of course this is all in the name of MPG. If you are not worried about MPG, you are not worried about any of this anyway!