I’ve got bleeding edge trunk (as of lunchtime yesterday) and once I installed it, I could no longer share my login cookies between WP and BB. I reverted to my backup and it magically worked again. At first I thought I must have whacked my bb-settings (since that’s how I thought I fixed it last time), but that didn’t work.
I’ve been fiddling with this a couple times, and I finally found my notes that my ‘working’ version of bb-settings.php was how I fixed it (basically I fiddled with it and now it works). I can’t use it, though, since if I try and paste up that file with the trunk build, the forums die.