He gives the good advice that you should only follow the rules when they make sense, and not otherwise. With that in mind, the two rules I disagree with the most are:
> Measurements should be mathematically related
> Elements should go in order of visual weight
Because, whereas most of the other rules are probably good to follow 90% of the time, these feel sort of arbitrary and opinionated.
I think making measurements mathematically related is a convenience and is often helpful, but for the same reason that optically centering things is better than mathematically centering them, I think you can easily ignore a mathematical relationship between values if it doesn't look as good. There is nothing inherent about humans that makes us prefer magic numbers, it's just that using them gives us an easy way to achieve visual consistency. If it stops doing that, ignore the ratio. If a grid or your font sizes look better nudged by a pixel or two in one direction or the other, do that instead.
With respect to ordering elements by visual weight, my only complaint is that he specifically says "heavier first", rather than "heavier first, or heavier last, both are fine as long as you're consistent". So, it's a nitpick, but it bothered me because it's an easy distinction to make.