What a waste of money! I did it during the peak of summer this year and it totally was not worth it. For the same price as the Fantasmic dessert buffet, we got to sit at the Golden Vine winery with a plate of bread, assorted cheeses, olives, grapes, meats, and a SMALL glass of vine. (They charge you for refills.) There's also a different box of stuff for kids. There were only three other parties participating in this.
Also, there were great spots available right across the winery until just before the parade started. In fact, if you sit on the wall across from the winery, about five minutes before the parade starts, they'll close the walkway and let you sit alongside the parade route.
Save your money for Fantasmic. Now that was worth every penny.