The unlockable characters seem to share spells, but I think they still have special bonuses. I just unlocked the Barbarian, and I'm getting criticals out the ass even though he's level 1 with the beginner's axe.
edit - I'm wrong, he just starts off with an axe that gives criticals. I assume that's what that cracked skull is in the blacksmith's shop.
Anyone else get that wooden club? +5 attack, +5 defense, -5 agility, level 20.