People argue too much about what genre it is.
It doesn't matter if its Pagan, viking, folk or black metal.
Ensiferum is just an awesome band and you should appreciate that. No... You MUST appreciate it. When Jari Maenpaa left Ensiferum, he was replaced by Petri Lindroos, and he's doing pretty good.
Music by Ensiferum can be fatal to emos, scenes and preppy mainstream girls.
Listen at own risk.