I thought long and hard about doing the Christmas party and ended up deciding against it.
From what I understand, everything they do during the party is available for free during the day at some point (except maybe the "free" cookies and hot chocolate). It basically sounded like the only bonus was lower crowd levels. I'm already going during a "lower" crowd level time, and couldn't justify the extra expense.
On top of that, I'm not certain DD will be able to hack a late night, enough to make it worth the extra admission cost, and I couldn't really fit it in with the dining plans I had.
Now, if we ever go during halloween time,
MNSSHP would be a lot harder to turn down.