I like w3t, I started using it this summer, unfortunately I have had som problems with too many users on my forum, it might be a problem with my mysql-setup. I am still working on solving the problem.
Before i used DCForum, not the latest version. It was pretty fast and the modified version I used hadled more users at the same time. It also has some features that you can't find here.
But it is only written in perl, and it uses flat-text-database and it is a pain to translate to another language.
If I can get w3t to work with many users and then put in some of the things I am missing from DCForum it would be unbeatable for me.