I think I like it. I can see where I'll get bored quickly with the Witches & Werewolves - but thankfully EPs typically also integrate a lot of minor features that just make my overall gameplay more interesting
(ie: Sliding Bookcase).
It'll probably be one of those EPs that grows on me right before it gets released like Showtime did.
I'm actually excited about a Zombie infestation in my game (like someone else said, the townies don't really affect my play that much) - I can't think of anything funner to do than to fight off a horde trying to take over my home! At least it'll be good practice.
I'm also a fan of Plants vs Zombies, so I already know I'm going to preorder to get all the cool (to me) PvZ extras! (As usual, I will wait until they offer a free SP to go along with the exclusive content).
P.S. I'm also on the annoying "I Want Seasons" band wagon and my heart drops every time a new EP is mentioned without it. *sigh* Someday my Sim World will be complete... I have a feeling it'll be the Last EP they release.