We have done the Dessert Party twice and would do it again, but it certainly is not for everyone.
If you reserve this, the #1 thing to know is that the ADR time IS PROBABLY WRONG. There is 1 and only 1 Dessert Party per night and it starts 1 hour before Wishes for all attendees. The ADR system still seems to treat this like a regular restaurant and gives people staggered ADR times. No matter what ADR time you get, you have a reservation for the Party and should show up 10-15 minutes before it starts. They check you in and give wristbands, then seat everyone right at 1 hour before Wishes. If Wishes is at 10, show up at 8:45 whether your ADR says 7 pm or 9:20 pm. The ADR is WRONG.
The first year we went the buffet tables were on the same level as the seating tables; this year the buffet was up on the mezzanine level so there were more seating tables = more attendees on the main level, but I did not feel it was over-crowded. Pushing/rudeness in a buffet line can happen anywhere, I guess. There were several long buffet tables with identical dessert items and they seemed to be restocked regularly so that should not be a problem.
You do not get much of a view of the MSEP, and if you go to Main Street to watch it first you will miss half the Dessert Party - seems a waste of $. If the Parade is a deal-breaker for you, save the Dessert Party for another trip.
I actually thought the Party worked better for groups without small kids. The desserts are more bite-sized (little tartlets, demi-tasse cups of creme brulee, chocolate-covered strawberries, mango shooters). There are cookies and rice crispy treats, but my feeling is that it is not directly aimed at kids. Beverages include hot coffee & tea, iced tea, milk, & lemonade. NO soda pop. Ice cream was apparently added during the summer but may be gone by now.
I think it is a great opportunity to sit down in real chairs and actually get to talk to your family/group without shouting, to nibble a variety of desserts rather than one big monster ice cream cone from the Plaza, and have a good view of the Castle without having to stand for 2 hours ahead of time.
Bonus points if you schedule the Dessert Party when the MK has evening EMH: the sugar high from the Party can easily carry you till that 1 or 2 am park closing!
Final note: please do NOT eat a TS dinner before the Dessert Party. I recommend a large late lunch instead. Figure that you should be finished with you last meal (finished, not starting) 4 hours before the start of the Dessert Party.