for about nine months we ran on a forum software that we'd written ourselves, and although it was actually quite good, i'd say comparable to some older version of vB and UBB, we were about a quarter of the way done with converting it over to a php based, mysql run system..
when we decided that we can't put in the effort that they guys at vb can, and we shifted over to a vb. that was a couple months ago. and we've already gained much experience with vb, i had some previous from other sites, but none of the other admins did.
we've already had our share of DB loss, style screwups, and other general mishaps. but we're going on 700-800 members, with somewhere around 30-40k posts, and constantly growing.
for example: last month we had 20k hits a day, now it's up to 40k.. and we've gotten 400k hits this month alone!