There's another interesting forum - I've looked at it and think it's a good solution for some, but I admit I'm using Active Forums for my main sites as it is robust. 

http://presstopia.com/dnn/Default.aspx?tabid=172  It's free, but also you can purchase for a few dollars and remove the ads and have some RSS feeds.  I think it's quite skinnable too. I have found Active a little harder to skin and maintain, eg.. an update seems to lose the work if it's not backed up, but this one is different.

Haven't tried it out on high volume but worth a look in I suppose for someone looking for another forum.

For high volume, I think that Active is probably still better since it's had commercialisation to help develop it further.. and as they say- nothing for nothing.... leaves nothing (some of the time and usually when you need it to work the most)

I think there are some very good features to this forum, but it's still needing some polishing, and Chris has done an outstanding job, so that can't be taken away from him either.

Nina Meiers