Great to have an official forum! +1
I'm personally more comfortable with forums over mailing lists - just easier to browse and I have enough trouble keeping on top of mail as it is. I'm sure the lists will continue to serve a vital need though.
More importantly, I suspect that the presence of a thriving (and friendly!) forum could do a lot to attract potential users who are checking out FreeBSD. It should help create a sense that there is a real live community out there, which in turn makes FreeBSD feel more approachable for the inquisitive/nervous. (This is of course predicated on the assumption that we welcome new users...

)
/sim