Thanks for mentioning the threading effect.
I have noticed, when a new message in the thread is clicked, it appears instantly. No waiting. Unlike the normal threaded message system.
Note to Dien: In addition to Ankesh's suggestions, might also pay to have a note which says, "Registration NOT required before posting" - if that is the case. Otherwise, people will think they need to register to post - or even read - and they won't do that.