From the Potter fansites' review of the food at WWoHP:
"It was thick, the fuzz, then rich, then colder and thinner at the bottom. A few more drinks and I was sure that the substance I was drinking was from another world. I don't know how they did it, but the butterbeer feels like it changes density as you drink. It's chilled, too - the butterbeer will be kept just above 32 degrees when it is served in the park. As for the taste, it is described as a cross between "butterscotch and shortbread" - I think that's probably accurate. I'll also say that I've become a fan of a personal homemade butterbeer recipe involving creme soda, rum and schnapps - but this, a non alcoholic beverage for park guests of all ages, far closer matches what is likely served in Hogsmeade of literature. What surprised me was that, the more I drank, the more I liked it. It is a solid beverage, a solid "brew" if you will, that has a consistent taste and is not too sweet or strange. It holds its flavor the whole way through, and let me just say the cream on top is excellent for giving the drinker a butterbeer moustache. I'm finding difficulty in describing it more, except to say that it must be tried and will not disappoint.
A frozen 'icee' version of the butterbeer will also be available in the park. After finishing our butterbeer, we tried it, too. It really is a testament to how solid a drink is, when you can make a frozen version of it accentuating the flavor that doesn't completely ruin it."