The #1 thing that keeps most users compulsively coming back to your site is to check and see if they've been replied to. The Pavlovian hook of "You've Got Mail!" was one of the keys to AOL's success. Users LOVE stuff waiting for them.
Presently there's no way to view all unread replies, aside from the emailed reply function (and emailed replies may work well for some sites, but, for a community site like mine, they spoil the magnetic attraction of surfing in to CHECK for replies!).
If new replies could somehow be listed on "My Home", that would be so awesome. It'd be a veritable tractor beam to users.
JIM