The biggest benefit for me was the complete understanding and model you get of the entire computer. How it works, what theories it is based on, why things are the way they are (in terms of the Turing model, the way microprocessors work, etc).
I don't believe this knowledge is helpful from a software engineering point, and I may have been a better programmer if I had spent those years learning more about how to work as a team and how to solve real-world problems. However, I do feel that it has allowed me to switch between different fields of programming without completely being thrown for a loop. It has allowed me to understand the issues that crop up when something goes wrong on a much deeper level, or why problems crop up on one part of "the stack" that I may not have understood had I focused merely on learning how to program. These are personally valuable to me, whether or not they may have been more valuable to my career.