I also have decent eye-sight and am 29, so I don't think it's an age related thing.
Anecdotally, I find reading large text to be a lot more comfortable. I don't have to strain my eyes to read.
This is a great post, at 100% zoom it was perfectly readable. HN by contrast gets zoomed habitually to around 150% on my desktop.
When viewed on the screens most people here are using, they're unreadable.
I find that 200% zoom works for Full HD screens (and is acceptable, if a little big, at 1680x1050)
I wish web designers would learn a thing or two from the writers of LaTeX.
I can remember when we used to optimize for 800x600.
The main reason I do this is to make the default font sizes for programs, websites, and OS's more readable without visual glitches or breaking layouts, as zooming has an unfortunate tendency to do.