Public discussions of life extension suffer from the confusion between two possible meanings of it.
The first meaning is to just postpone death. Maybe at 90 you don't remember anything any more, the list of your chronic diseases doesn't fit on a page, you require round-the-clock care and semi-permanent sedation, take 37 different pills and need a trip to the hospital weekly -- but by golly! we can and will keep you alive for ten years more and as medicine progresses we'll keep you alive for twenty years more.
The second meaning is to postpone senescence. You're 90, but you look like a 60-year-old. You're mobile, active, with most of your mind intact, with a functioning immune system and ability to enjoy life.
I feel these scenarios are rather different. In particular, they lead to different answers to questions about whether life extension is worth it.
I once heard an acquaintance of a friend of mine put it this way (back when I wasn't familiar with transhumanism and I didn't know whether he was wrong or right): “Life extension had better be called old age extension: you may die at 160 instead of 80, but it's not like when you're 40 you'll do the things people today do when they're 20.”
Anyway, going by revealed preferences, fewer people might dislike the former scenario than you might think.
This new study by Pew Research on American opinions about radical life extension turned up some interesting results:
I also find the demographic splits on page 3 to be surprising. On the question of whether treatments to extend life by decades would be a good thing for society, whites are significantly less likely to agree: 36% of whites agree whereas 48% of Hispanics and 56% of blacks do. There is a negative correlation with age (48% of adults 18-29, 46% of adults 30-49, 37% of adults 50-64, 31% of adults 65 and older) and with income (47% of those earning 30k and less, 42% of those earning from 30k-75k, and 39% of those earning 75k+). The income result in particular surprises me, as my intuition was that people with a higher quality of life would be significantly more pro-life extension.