One of the things that I found was lacking in the old board was the fact that it was not possible every time to identify the post to which a subsequent poster was replying.
If possible, it would be helpful if a feature could be designed in that shows something like "this post replies to post #" or something similar, even if it's in a "hidden" field.
Don't the levels of indentation tell you that? Granted on a busy thread it can get a little hard to tell as the original can be pages away. I have my monitor (old Viewsonic which is rotatable) in a vertical orientation so it may be easier for me to see more message summaries in the thread.