A little more information...
On the day of the party, MK is open to "regular" guests until 7 pm. However, guests who have tickets for the Pirate and Princess party were admitted and given their wristbands as early as 4 pm that afternoon and are free to enjoy MK with the regular guests before the start of the party. The Wishes fireworks show, which is usually much later in the evening, is put on just before the closing for the regular guest. Shortly after Wishes is finished, guests who are not wearing the wristbands for the party are ushered out of the park. There are many, many opportunities to see characters and many of them are decked out in pirate attire. There are also special photo opportunities (e.g., Cinderella's carriage). They run the parade twice and also had a special fireworks show for the party.
For us, it was definitely worth the money. We didn't use any park admissions from our MYW tix the day of the party...so, the price of the party tickets was in lieu of using one day's admission.
We had a 4:00 pm reservation for an early dinner at Crystal Palace, finished dinner by 5:30 pm, went on some rides, went to main street to watch Wishes, and then the party began.