I used to like the way Nick.com did its forums in terms of replies. It was nested, like dA's, but each comment had a subject line you'd have to click to read the comment. Although it was definitely tedious to have to click to read all the replies, it was convenient for things like fanfiction topics.
I really like how dA looks in terms of replies when comments are nested; it's very easy to follow conversations. Most regular forums, like Invision and ProBoards (are those all out of date? I don't forum much anymore), don't differentiate which comment you're replying to without using the "quotes" system, so it's nearly impossible to hold multiple conversations.