I want a modern forum solution NOW. So I decided to make the mistake (hopefully not) to just run it from the first alpha to the last version available to me. XenFans went live with beta 1, which went great, followed by WeTalk with beta 1. Also went fine. Few bugs found, reported .. some fixed, some pending. It's all good.
Going from vB3 to vB4 would mean a huge compromise, having a few bugs as minor compromises is something I can live with. XF ftw. huzzah