I didn't agree with all of it. I had (and have) an attitude that goes along with the science fiction I grew up with: seeing the material world as a series of problems to be solved. Illuminatus! is a polyvocal work that doesn't give Right Answers, but my approach was more likely to be associated with the bad Illuminati, while the good guys were more likely to identify with the part of themselves they share with the material world. I thought about that, I learned from it, and I still don't agree with all of it.
The book programmed me in ways that were not obvious for months, even years, just as it had promised. I started something called the Illuminatus! Nut Cult because nobody else had. I joined fanzine fandom and corrupted as many of them as I could. I fell in love with a Lovecraftian, and remain with her. I met the authors, whom I liked, and I read and enjoyed later work by them. They admitted that the book was half bullshit, but they were never sure exactly which half. Me neither.
Tom Jackson has a site called RAWIllumination that will begin an online reread of the trilogy tomorrow. You are all invited.