As someone who has gone down the rabbit hole of measure theory, functional analysis, and the like, I completely agree with the wonderful balance that Prof. Osgood strikes.

For a concrete instance, he brings up the distributional viewpoint of Laurent Schwartz and talks about the class of decaying functions for which one can operate nicely. This was something I next saw primarily in mathematics texts, with very few engineering books caring to talk about this even though it is not very hard to introduce and gives significant clarity to the process IMHO.

Studying Prof. Osgood's stuff off Stanford SEE during my summer vacation at the end of high school was one of the best learning experiences I have had till date.