Ning works, but what is its future?
I am considering moving this site to BuddyPress. The major hurdle would be moving all the content (not just the member data)
Well, you have a small army of web developers here, I'm sure some would be willing to lend a hand.
Can I assume you've seen this? http://teleogistic.net/code/wordpresswordpress-mu/import-from-ning/