I'm not GP, but I read and worked through almost the entirety of Volume 1. I found it both approachable and enlightening. I have read (but not worked through) large chunks of Volumes 2 and 3, I have not purchased a copy of Volume 4 yet.
Volume 1 really works well if you also work through Concrete Mathematics (my professor and I started on Volume 1, diverted to CM, then back to Volume 1). CM provides enough additional math to get through chapter 1, where I was having a bit of trouble on some of the math heavy portions.
Fair enough, I don't have the time anymore myself. College and my mid-20s were the best time to do all of those things. Now that I'm approaching 40 I have very little time and have to be more selective in how much time I dedicate to these kinds of resources.
I actually started working through TAOCP one summer during a very boring sys admin job. I couldn't actually change the system to improve it, just complete whatever tasks were given to me and help customers. Maybe 1-3 hours a day of actual work effort. And in the pre-smart phone days, a book was easy to work through without distractions until the next ring of a phone call or ding of an email.
Volume 1 really works well if you also work through Concrete Mathematics (my professor and I started on Volume 1, diverted to CM, then back to Volume 1). CM provides enough additional math to get through chapter 1, where I was having a bit of trouble on some of the math heavy portions.