Spoiler warning
I agree that the last book was extremely disappointing. No twists that fans hadn't already anticipated (I had expected that RAB would not be Regulus Black because it was so obvious. Harry being the horcrux as well as Snape being good were other plots that had already been widely discussed ). She has delivered far better surprises in earlier books - Sirius being good in the third book, Moody being the impostor in the fourth and Dumbledore dying in the sixth.
Too many inconsistencies, unanswered questions, convenient one-line explainations to inconsistencies (why were Ron and Hermione able to open the Chamber of Secrets to retrieve the fangs - only the Heir of Slytherin should be able to do it, not speaking Parseltongue), people dying needlessly and by the hordes and worst of all, Voldermot seemed impotent and stupid, chasing after Harry, no longer the dreadful mysterious character that arose in the fourth book. I expected a more plausible explaination to Petunia's readiness to take Harry in after his parents death. The part about the Ministry of Magic and the infiltrations and their Muggle policy was quite annoying. The epilogue was almost fake.
JK has done much better in earlier books, but failed to deliver a fitting end to this great series. To her credit though, she did her best to tie all the books in the series together, referring to several characters and instances in the earlier books, but the tie-ups are so loose, that they feel like forced attempts to be clever rather than a carefully planned plot.
I expected the treat of a lifetime, but the book was not a worthy follow-up to book 6, just wasn't worth staying up all night.
That said, JK did pull some important moral issues together, about the choices we make and the consequences of those choices. The Hallows vs Horcrux choice, the choice to treat non-wizards with respect, respect life no matter how wretched, keeping the faith and staying on course and sticking with your friends. I also like the twist about DD owning the elder wand, that was unexpected. I am going to read the book again to see if i like it better the second time.