Well my hosting site, (over 100,000) hits our forums are the biggest part of em all. We have tried SMF, and alot of the others forum systems but none of them can compete with MyBB.
www.netwebhost.org/forums
I wouldn't use that vbulletin like theme .. not because I don't like the way it presents the content, but because the colours are ugly. VB has a weird colour scheme (that dirty "violet" and the blue .. don't know who told them this is a nice match). You can use the structure from that theme and try to modify the colours and images to best suit your forums. Don't be afraid to work the layout. it's not that hard. Best of luck with the project and please keep us posted on any updates
i have also tried using others like smf and mybb much better.