I'm pretty happy with the forum, it's nearly reached the level of use the old one had and I'd love to see it leave that far behind.
It's not membership numbers that count, it's active members - for some reason I seem to have 2-3 people sign up per day, never post a message, and are never seen again. The old forum had lots of registered members but few regular visitors...
I put links to the forums on the main page of the site, and that seems to help encourage traffic.
Of course, right now page 3 of the Subject page for "Love" gets more traffic than the entire forum, but that's life I suppose.