I have used phpBB and I think its great, good community, great addons and themes.
Demo : free forums

phpBB all the way, if you're not super proficient at it, it might take a bit of research to figure out how to do something but in my experiences it turns out much better.

From the user standpoint though, it really just depends how much work the Admins are willing to do behind the scenes, you can make any of those systems look polished with all the special bells and whistles.
Demo : free forums

I definitely prefer PHPbb they have a bunch of add-ons and design templates that are also quite good.
Demo : free forums

Among the open-scripts one, I have used both phpBB3 and SMF. phpBB3 always takes the lead. It has got more mods, themes etc. On the other hand, SMF doesn’t give you much features as compared to phpBB3.
Demo : free forum hosting

I suggest trying out phpBB. phpBB 3 is by far the best forum software I’ve ever used, it’s open-source so it’s free to download and use. It’s simple and doesn’t include all the “unneccessary” features you speak off. It’s minimal. Vanilla doesn’t even come close to competing with phpBB, so yeah - give it a try.

Just try it out on this host : create a forum

Among free and open source software, phpBB tops my list. Fairly good product, huge MOD database, and pretty good support.

If you haven't got much time, and want to see what the new phpbb3 can offer, just try it out on this host : create forum

Hope this can help!