The median Silicon Valley techie ego surpassed 1000 millizaphods several years ago. Many of the Bay Area locals are already immune.

I thought the reason he survived wasn't that he just had a huge ego, but because that universe really was just created for him. Or maybe I'm misremembering that part?

You're right - by crawling out of the wrecked building through the window he entered a pocket reality designed to help him discover the true ruler of the universe. Or something.

I can't remember whether it happened that way in the radio series or the books as they're quite different (let's pretend the film never happened).

It was in the books because that's how I remember it and I never listened to the radio series (I also try to forget the film exists).

Um, wasn't that the whole point of the machine? It would strip away your self-deluding beliefs, and give you true perspective? In other words, no it isn't good enough to just think that the universe is created for you, the machine will kill you in that case. You actually need to have the universe created for you, and only in that case will you survive the experience.

I suspect many folks around here are pretty well immune to true perspective.