Ok I'm going to put down my impression of the book before discussing what other people have to say.
I thoroughly enjoyed the entire series, though I was never really able to get through the third book (found it boring when I was a kid and never got around to rereading it). The first two were pretty good, albeit being somewhat brief and seemingly underdeveloped, but as the series went on it matured greatly and appealed to me even more. Deathly Hallows is obviously my favorite, followed closely by Goblet of Fire, then tailed by Half Blood Prince. Order of the Phoenix was horrible, comparatively, and reading it was almost a chore.
Anyway, onto the seventh book. It was structured rather differently (no Hogwarts) and throughout the beginning of the book the mood was rather lonely. Because of this, Rowling had a lot of time to develop the three main characters, further rounding them out and feeding dynamicism into them. Also, the concept behind the book was pretty complex, and as Harry would take time to ponder over things, more and more would be revealed and Harry himself really seemed to grow up. The delivery of Harry's thought processes was done very nicely, and I found that as my own thoughts of the reading quickened during those "Eureka!" moments, Harry's also became more and more abstract, fragmented, and seemed to fit perfectly. The pace of the book could use a little help, as I sometimes found that parts would drag on and on (like the camping scenes) and others went a little too quickly, but it didn't really affect the impact of the book itself.
The characters were all portrayed very well, though I thought several of them could use more exposure (again, due to the fact the main three didn't attend Hogwarts this year). I personally think that the characters themselves were what really took hold of me throughout the series, and since I'm about the same age as Harry and the gang, I was able to easily relate to them as we all sort of grew up together. This time around, Snape was by far my favorite character, and the way Rowling was able to turn him from a hated murderer to one of the bravest and noble characters in the book was fascinating. "The Prince's Tale" was one of my favorite chapters of the book, and reading it ran chills up my spine and brought a tear to my eye. Dumbledore was another rather intriguing character in this book - in all the previous books he represented that single, untouchable character who was the epitome of Good, up until his final moment at the end of book 6. However, being able to delve into his enigmatic past turned Dumbledore into a much more dynamic character than he had ever been, bringing him down from his god-like status to someone with feelings and flaws just like you and me. Otherwise, Harry, Ron, Hermoine, and the rest of the lot, though still loveable, remained rather predictable.
As for the ending...I had fully expected Harry to die while taking down Voldemort and what ended up happening sort of took me by surprise. However, I do believe that Harry's death would have put a lot more meaning behind his decisions and actions, though I would've been greatly saddened at the same time (yeah I guess I'm still a kid at heart). The ending seemed like a huge relief, knowing that everything turned out ok, which is I guess what Rowling was forced to intend for the well-being of her audience. Nevertheless, the ending wasn't nearly as important as what had occurred throughout the book and what had been revealed, so either way I wouldn't have been disappointed. The epilogue was largely unnecessary, though I do think the whole "Albus Severus Potter" thing was kind of cool.
So yeah, those are my thoughts on the book. After finally finishing it I was actually kind of sad it was all over...Harry Potter was something I had grown up with and had no less attachment to than an old pet or a favorite teacher. Now I'm probably going to read through the sixth book again. Then the maybe I'll read the second one again. And I'll probably find time to finally get through the third...