You will probably get replies that vary a lot. People either really like it or think it is a huge waste of money. So the question "is it worth it?" is something only you can decide.
We have done it twice, and have booked a third time for the end of August.
We like it.
But, you cannot see the parade well from the party. You see the tops of floats from a distance, and hear the music. If you are interested in seeing the parade well, and only have one night you can be in the MK at all, the dessert party may not be the best place for you to be on that one night. Our first party, we did check in to the party at 8:30 and got our wristbands (party was not open yet, but you could get bands early). THen we rushed to Main Street to watch Spectro, then rushed back to the party. THe party had opened at 9:00, and we got in around 9:15, but most desserts were still there. People had taken a lot, but they were well replenished. Wishes was at 10:00.
So it was possible to do both the parade and wishes party, but IMO, it was too much rushing and too stressful to do so, and avoiding stress is the reason to book the dessert party. Last time we went to the MK on more than one night so we watched the parade one night and did the dessert party the other night, and that worked well.
But if you only have one MK night, I would probably skip the party.