Let's face it - the Discussion Group feature in Sharepoint is not the greatest in the world. Yes, it's functional, but for those of us used to spending a lot of time on BB's, it just doesn't measure up.
Until someone releases full-fledged BB software for Sharepoint the best bet is customizing the existing list template. Serge van den Oever has a good implementation that he's been kind enoug to share with the community. Check it out and let him know if you like it.