I read this book when it first came out, and I pull it out every now and then and re-read it because I enjoy it. I thought the idea of "recycling" the elderly was intriguing; I don't know if I could make the choice to leave everything behind forever, but the lure of starting over in a young body would be a powerful one. Especially since the only alternative is death. In the right mood, it might just be a what-the-hell decision.
I had no problem with John Perry's internal "voice". Don't know about the rest of you, but my internal voice is not commensurate with my actual age - sometimes I don't think that I've advanced beyond age 12.

I don't think that one necessarily thinks "old" when one is 75; we may assume that people that age do, but I figure that if I'm still goofy at this age, further ripening isn't going to change that. I think that the outer shell tends to mislead people.