Not to mention that most sites will put their main content into a container with a limited width anyway, since overly long lines are awful to read. So unless you're using the browser side-by-side with other content on a low-res monitor it's a net benefit. And even if it's not I usually find the extra vertical space to be worth more, as you said.

i get where youre coming from, but imho the eye tends to parse information more effectively if delivered vertically, since it knows it that way from other media. just my personal opinion though.