A great post, and one I definitely would have benefitted from reading before taking on my current, and first, PM role!
One point you made that I would like to expand on, only because there is an aspect of it in my job that surprised me, is that as a PM you'll end up doing many things yourself. In my role, I've found that this is often true as an intermediary step on the way to a long(er)-term solution; in many ways, this is my favorite part of what I do. If something needs to be done and there is no one to do it, then it's on me to handle it as a containment until a solution can be created. That can mean hiring someone, delegating it to a person or team, or creating a system that simplifies the task to the point of triviality or negates the need for it altogether. Regardless of the outcome, you get to become the expert in that thing before passing it along or reducing/eliminating the need for it. This is both extremely interesting from a work perspective (variety is the spice of life, and all that), and also a great way to learn the whole of the project as if you were a quilt maker -- looking at the large and small.