I'm currently playing a 'normal' human legacy/neighborhood and often forget that SN is even installed.
Otherwise you really aren't missing out on anything. If you like/plan on playing the supers or like gothic aesthetic, definitely get it. The zombies can be a pain every full moon, but there's multiple ways of disabling them. So, unless you specifically play with supers, you will almost never even notice this pack.
Supernatural really only adds the supers, improves vampires from Late Night, and adds gothic furniture/clothes. IMO, Seasons, Generations, and Pets are must haves for everyone, in that order.
