It felt very true to the novel but a couple of little details were changed that I thought wouldn't really have needed to be changed. I liked the way they filled in some of the research...what took chapters in the novel was easily handled in a few short lines of dialog without seeming forced in. And it was great to finally meet Bill Weasley even though I've always thought they should have introduced him and Charlie more in line with how they were in the novels.
They JUST introduced Bill?!?! WTF? He appears WAAAAAY before the last book.
I'd love to hear about the other discrepancies, because that stuff pisses me off to no end and may ultimately decide whether I waste my money on this or not.
If you're stretching one book (not even the longest one at that) into TWO movies, you damn sure better include everything IMO.