Well, SMF makes it really nice and easy to add plug-ins and enhancements. It also makes it easy to back up the forum should there be a forum mishaps (hasn't happened yet **knocks on wood**). But yeah, adding the Youtube and other items has been pretty easy. I haven't really dabbled into plugins that do anything all that difficult. I do not want to overload the forum with features that will not be pertinent (and would end up just weighing it down).
Once the new version of the SMF engine reaches a status past "BETA", I'll be upgrading.