Bellatrix walking on the table in the Great Hall is such a class addition! I don't think she's even there in the book (I may be wrong, it's been a while). It's good to see Quidditch is included here for one last time. I'm sure the effects will be much improved from years ago. They needed to bring it back because there's not much action in Half-Blood Prince.
That's also why they've added an extra Death Eater attack at the beginning, when Harry is staying with the Weasleys. I always thought one of the shortcomings of the books was how Harry just went back to being safe at the start of each one (this was explained away at some point by Dumbledore saying he placed a protective charm around him, or something, so he can't be harmed, it always sounded like a bit of a copout from JK Rowling!)