I'm going to try it when I go. It sounds yummy, but then again I have a massive sweet tooth. It's chocolate cake layered with berries and cream.
Trifle (Not nescissarily this type but the dessert type in general) is mentioned a lot in the Potter books and is a popular dessert over in Britian. It sounds good to me.
I say try it. What's the worst that could go wrong? Anyway, if you don't like it, just go get a cauldron cake and have that instead.
If you don't try it, I'll post a bit of a review of it and the Three Broomsticks (As that's the only place we're eating) after my trip in a few weeks (So excited!).