Urgh, that one's always such a dilemma for me. On the one hand, berserk is less accurate than attack, and being cursed means no extended or ranged capability. On the other...extra attack (or even two) for massive damage.
Actually gave it to my Fighter last playthrough, and kicked enormous ass with it all the way up to the Sorceress battle, when I could replace it with Fang (and later, Fang with Excalibur).
"You will not forget this devil's power! You are not worthy as my opponent..." -Vergil