To be able to view all posts in a thread in the same page.
I, personally would like that (<1sec downloads on a T1), however, I see many posts reflecting slow internet connections. For these members, downloading all of a 33 post thread every time may be a hindrance.

another problem here would be that many threads divide into 'subthreads' (just look at this one) so where would those new posts be located. On the Keil site where all posts are on the same page an answer to post 2 will be inserted before post 3 and I, for one always miss the new posts that are not at the bottom.

Erik