I think my first forum was IPB v1.3 and v2.0 (before it became commercialised) and then tried installing SMF - which I found a little tedious to use - and then read about MyBB. The rest, as they say, is history.
If I ever have to integrate my site with WordPress properly, I might consider
Simple:Press - it's starting to look very good.
I started with Ipb 2 but after a while I wanted to go with a different forum for my new forums and tried MyBB. The software itself was good but I didn't like the community much. When my forums grew considerably I had them moved over to Ipb 3.
I used Ipb then converted to MyBB and now I went back to Ipb again.
I used IPBFree at first then MyBB.
MyBB, phpBB3, ForumGratuit...
I used mybb in my first forum and it awsome and need some plugin hope will get from this site sees with awsome plugin
My first forum, I have tried phpBB 2, but I think it is too complicated, because I did not know Forum squatting, coding and so on. SMF and then I try to stay with it because I found the package manager is easy to update and install plug-ins.