The book reminded me of the 5th book in the series where the story just seem to lose momentum at certain points. Also there was much attention focused on love triangles and the students relationships with one another and I just didn't care for too much.
This book also mostly centered around Harry and Dumbledore and learning of Lord Voldermort's past as Tom Riddle. I liked this part best because it does shed some light on Tom Riddles character.
We also learned about Horcruxes and there role that they will play.
Oh and yes the last 5 chapters are by far the saddest parts to this book. I didn't cry but that's because I'm not a huge fan of Dumbledore. But Harry is now truly alone all of his guardians have died and he now faces the task of destroying Voldermort all by himself.
The 7th book should be promising and I hope that Ms.Rowling decides to tie up all the loose ends in the series.