Yes, I did CRT breakfast at the castle last Sept. with my two daughters who were 7 and 3 at the time and my mom. We booked it again for our next trip this coming Sept.
It was wonderful, I thought the breakfast food was good, and I like the fact that the breakfast is cheaper than lunch or dinner, so that works out well. We got to enter Magic Kingdom early, we had a 9:00 a.m. ADR and MK opened at 9:00 that day. We were early for our ADR and they still sat us right away. I got beautiful pictures of the girls in their princess dresses in front of the castle on a basically empty main street.
They pour your coffee, juice, etc. so really a sit-down meal. The photo is included in the price, as well as tax and gratuity. Ther service was excellent, albeit very quick. They don't necessarily "rush" you, but they are pretty efficient about getting your food out quickly. I think they like to move this place along to get the next diners in.
The only negative I would say is that I actually met more princesses at Arkeshus. We only had Cinderella who stays downstairs for pics, and at the actual meal we had Snow White, Sleeping Beauty and Jasmine. I have seen others who say that they had four princesses at the meal in addition to Cinderella downstairs. Not the case with us.
However, I told the girls we were only going to do one breakfast this trip. So, I asked which princess breakfast they would rather do, and they both said the castle.
Oh, and I forgot to mention, the girls did get a magic wand and a wishing star, which was included in the price of the breakfast as well.
Have fun and enjoy your trip!