vBulletin was a software that I moved to after I used MyBB. My forum was doing well and I wanted to bring more to the forum at the time, with all the features vBulletin had at the time and there being no Xenforo at the time of me switching, I switched to vBulletin.
I loved vBulletin 3 and was able to do so much with the forum I had at the time. When they updated to 4 it was something I wasn't so keen on anymore and was happy when Xenforo released and moved to that.
Nowadays it is very rare that I see people on vBulletin, most are either on Xenforo or using free-hosted now.
Do you still know anyone who is using vBulletin?