Instead of xml-rpc pingbacks for 0.84 I'd love to see a more useful feature - OpenID support
Apparently wordpress.com has had openid support since March:
http://wordpress.com/blog/2007/03/06/openid/
and here's a wordpress plugin to allow logins via openid, now we need to port it to bbpress...
http://verselogic.net/projects/wordpress/wordpress-openid-plugin/
This would allow the quarter-million wordpress.com members and 120 million other openid participants to post on any bbpress forum with verified authentication.