Although I know C++ I do not use it daily as I am more of a plan old C guy, but reading the guide helped me uncover some (hidden for me) decisions made in Swift and I really enjoyed reading it. And this is after using Swift on both client and server side since version 3 and after reading all the Swift guides and watching all Apple WWDC swift videos (multiple times).
I agree. I don't know C++ at all (and barely any C), but I found Doug's perspective very interesting and much as I find TSPL very useful, there's a compactness to these posts that has its benefits. Also I learned from one that you can have a default when subscripting and there's no matching index.
Agreed, and I wish there were more of "X for Y practitioners" books. A lot of the times studying a new language feels like a 40% waste of time when the same concepts could have been explained in terms of another language you already know. In my personal wanted list: "Kotlin for Swift practitioners", "Rust for Swift practitioners" (or replace Swift with C++, still fine).
I wanted to publicly thank @Douglas_Gregor for writing the "Swift for C++ Practitioners" blog series (specifically "Swift for C++ Practitioners, Part 1 - Intro & Value Types" | Doug's Compiler Corner 44). Even though I primarily work with plain old C and not C++ on a daily basis, reading this guide helped me uncover some of the underlying decisions made in Swift that were previously hidden to me.