Today's Los Angeles Times had an interview with Steve Kloves, who adapted the screenplay for the movie.
Article link
here (not sure how long it will be online).
Interviewer: What, if anything, can you say about the climactic moment between Snape and Dumbledore? In the book, it’s a short but intense scene.
Kloves: It is informed by everything [Potter readers] have come to know is true. So if you watch the film carefully, there are performance moments that are quite extraordinary, Alan Rickman [who plays Snape] especially. There is something we added that you can look forward to, a short scene between Harry and Snape prior to the big event. It’ll be interesting to see how it plays to the audience. It should be a haunting moment for Harry. While I was writing, I just had a notion about a moment between him and Snape, something Harry could look back on and question as to why he didn’t act differently.
Interviewer: I've also read that most of Dumbledore's pensieve memories of young Voldemort, then Tom Riddle, have been cut from the film. (Not to mention: Dumbledore's funeral!)
Kloves: In my original draft, I had every single memory but one, I believe. I even dramatized a couple of things that weren’t in the book in terms of Voldemort, like the death of Tom’s parents, things like that. I'm a Harry Potter fan, so my first drafts tend to reflect that, in that they tend to be long and all-inclusive. When [director] David Yates came in, he had a very specific point of view, which was that he wanted to showcase Voldemort’s rise without getting overly involved with his past as Riddle. He didn’t think that most of the memories would be as compelling on-screen as they are on the page. He liked them in the script, but he really felt that in the movie experience Voldemort’s story was more important than young Riddle‘s. We went back and forth on that for quite a bit. But he was very convincing, and I think it wound up working out well.