The same people who say SO has "a poor UX" are the same people who say that Reddit has "a poor UX". They're conflating gradients, rounded rectangles and text shadows with a user's experience of the site.
the use case is rather different, though: Hacker News is a list of articles other people have written with discussion and commentary. Stack Overflow is a list of questions from your peers with potential answers. (Also, that's a really old screenshot)
Quite the opposite. I find SO's interface very busy, and wish it was a little simpler, closer to Reddit. Ultimately it's the community that makes it, and the UX is fairly irrelevant.
