I in the other hand, with "below average" connection would love "all posts in one page" version. I mean, the menu bar with all the links, commercials, the headers etc add so much overhead that I wait quite long for each separate post to load. I'd definitely prefer to wait longer ONCE than to keep waiting with each new post.
Best bet would be a pref how to view threads, so everyone could pick their preferred method. I personally would definitely go with the "show all at once" one.