I have, twice, and I reccommend it to everyone!!
(But it's not specifically a "tea" party--- though that's what I drink. There's coffee, soda, juice-- lots of beverages.)
The display of desserts is wonderful! And there's a PHotopass photographer there, to get pictures of your family with the castle-- and no bystanders-- in the background.
But for me, the highlight is that I can enjoy Wishes in a SEAT, with no jostling for a place. Tinkerbell flies literally right over your head.
It's a wonderful evening, and well worth the money in my opinion.