We have been to a Mickey's Very Merry Christmas party every year for as long as I can remember, sadly over the last five maybe six years they have taken more and more of the perks some small (such as the free buttons and photo sent home) some much bigger in my opinion (removal of Twas the night before Christmas show and allowing many more people in to the park than years past).
Last year we decided to skip it, and from my whole families perspective, we didn't miss much, free hot chocolate and cookies, sure it wasn't the same not having those.
Other than the Christmas parade being shown at night time during the party which is a better experience (it is shown during the day to normal ticket guests) we were still able to see everything during a regular day.
I think if we had skipped it for a year ten years ago, we would have missed it greatly, but the events have been watered down so much these last few years, the benefits really are not there any more.
And I would like to emphasise although there are still a limited number of tickets sold, this is still a great deal higher than they used to sell, two years ago for example Space Mountain still had a two hour wait at eleven o'clock at night during a party and the crowds were very heavy. Where as years ago, there parties were a great oppertunity to almost walk on each attraction with minmum wait times.
If someone is going for the first time, and have never seen the Christmas parade before, it is great to see it at night, it feels that much more special in the dark, for people who have seen it before, just having the parade at night is not enough to justify the ticket cost of the party anymore without the other perks from before. (All in my opinion of course)
Even Holiday wishes can be seen by regualr park guests as we get closer to Christmas.
For us as a family, we don't see ourselves attending again unless there are some significant changes and perks to it again, it is a shame because it had become a tradition for us on the first day of our holiday each year to attend the party and get in the Christmas spirit.