Like whatshisface really being a good guy devoted to protecting Harry the whole time. If this was hinted somewhere, let me know, but otherwise, that just sounds like some poor cliche writing.
Well the only hints I can think of is how Dumbledore was always "I have something which causes me to trust snape no matter what and i won't tell you because it would be spoiler"
I didn't mind the book as a whole, I felt she crammed way to much in though and you just felt overloaded with information (some of which you really didn't care about) The final battle was probably the most. anticlimactic. thing. ever. and the Epilogue made me want to throw up. Fair enough she want to tell everyone what happened bu "albus Severus"? eugh. I'm less interesting in their kids name and more interested in what their jobs are, and what happened to the weasly wizards wheezes after fred died, also who's the new minister for magic and the new headmaster of howarts amoung alot of other things which jk didn't include.
In terms of her writing style I know alot of people say its badly written, i think this is due mostly to her conversational style, which is also what makes it such a quick read. If you go back and read the first book, you'll notice the child like voice which she uses really adds charm to the simple style, which I think is why the first book was so popular, however from about book 3 on this voice was lost and most of the charm in her writing was gone. Plus she has habit of writing things stupidly as if trying to sound intellegent ("it was not I who killed you Albus!"). (btw all this is based on cretaive writing course I've done through uni and not just random dirbble.)
I also agree with one of the earlier points in this thread about the story gowing downhill since book4, before then it was all magical adventures and them solving mysterys and such but then when voldemort came back it was all angst and darkness, Hell I'm fairly sure somewhere in the 6th book it says something like "harry didn't feel excited like he would have in his first year with a mystery to get to the bottom of" or something simillar.
Also it shits me that Sirius never came back. Every Father figure Harry's ever had has died and Sirius was the only one who seemed slightly plausible to come back because of the manner of his death. Hell even his uncle figure (lupin) died. which I think was a cop out easy way to get out of dealing with the werewolf thing.