I did it twice and really enjoyed it however a lot of other people think its not worth it as you already have your breakfast included anyhow.
I think there are 2 time slots offered
The first time I went we went for the first slot so we could have breakfast and then get into the park.
The second time we went for the later slot - went into the park for EMH then out for a leisurely breakfast and browsed in the shops before going back into the parks
I much preferred the 2nd slot as I felt more awake to enjoy the food more, didnt feel as though we had to rush to get into the park as we had already done some rides. Because of this we lingered over breakfast and so had extra character time as well as others were rushing out.
So if you do it think about which slot you would prefer as well