I have found it generally very uncomfortable because a vast majority of content on the web doesn't scale well vertically. You keep a wide window, you get way too long paragraphs that are hard to read as your eyes jump between the lines and whatnot. I've seen a couple excellent designs that do new columns as content comes, and there's only vertical scrolling. The columns are like 40-60 chars in width, as they should be. It's nice, accommodates the today's wide screens super well. But a majority of sites, HN included, are way wide for content if I browsed them in a 1920x1080 viewport.

HN specifically, if I have serious reading to do in the comment section, I might narrow my browser down to 600px for even better readibility.