Font size too big

I have a fluid site design that enlarges text font-size to keep the line length within acceptable parameters (70-80 chars).

It seems fine to me but for many people they complain that the font size is too large on full HD screens. My screen is larger than full HD and it looks fine to me. Is it actually harder to read large font (30px - 40px) or is it just a matter of getting used to it?

Should I keep the enlarged font size or do the traditional keep small font-size but enlarge margins.

Edit: Thanks for all your answers everyone, I get the general trend is that there is a too large font size. What I'm still missing and what I would like to hear is an explanation of what too large font size is, how to calculate it, its relationship to screen distance and screen size, and why it's too large, and so on. That would be really educational, thanks.