If you haven't seen it yet, I highly recommend you do! Like many others, I love the books, and the books are always better than the movies, though the movies are great too. This installment was was one of my favorites in the series, though it was not without some flaws. (Side note: Deathly Hallows is probably my favorite book in the series, so that might have something to do with why I liked it so much.)
Being only Part One, I missed seeing a lot of characters/locations from the previous books. This was the first movie where none of it takes place at Hogwarts! And a lot of supporting characters who I love didn't get nearly as much- if any- screen time. I believe Draco Malfoy had a total of one scene, and most of the Hogwarts students- such as Neville Longbottom- weren't even in the film. I guess I'll have to wait for Part Two to see them.
Unlike some, I really appreciated the decision to divide the movie into two parts. This movie felt a lot less rushed than other movies based on books. They weren't trying to cram 700+ pages into two hours. That decision was reflected well in the movie- we got to see more character developmen. The relationships between Harry, Ron, and Hermione were the central focus in this film. I think we saw those three characters- and only them- on screen 90% of the time. It's an important part and it wasn't rushed.