Here's what I think (broken into easily-digestible and highly nutritious parts):
Ginny and Harry/Ginny (aka "The ship that sailed a thousand deranged letter-writing campaigns"): Ginny was great in the book. Occasionally annoying, fairly bitchy and sometimes her uber-kewlness got a little too much ("Look, Ron's baby sister! Awwww....damn, she's hott! And athletic! And funny! And all the boys like her! And she smells like flowers!") but overall, a pretty solid character. I liked Harry and Ginny's little "thing". It was sweet and fairly enjoyable and it's so damn obvious that they'll get together again next book.
Ron, Hermione and Ron/Hermione (aka "The Green-Eyed Monster...No, Not Harry"): Very cute, very dysfunctional and very, very, very, VERY overdue. If they keep going on like this, I wouldn't be surprised if Hermione spontaneously combusted from sexual repression or just went up to Ron and shagged his face off. On the flip side, I actually liked Hermione in this one. Less the shrill, arrogant, "Shut up, it's good for you!" fiend from OOTP and more an actual teenage girl. Who woulda thought she had it in her shrivelled old-maidish soul?
Malfoy (aka "I do have a soul. No, really."): Both happy and annoyed. Happy, because the weak, spineless, cowardly BUT finally three-dimensional creep is adorable, for Gods' sake (and Harry's obsession made my perverted heart sing). Annoyed because I was wrong. Still good.
Tom Riddle backstory (aka "I AM EVEEEL! Hear me roar."): Meh. Eleven-year old Tom Riddle is really well-portrayed and the Merope stuff was cool.
SNAPE!: HOW COULD YOU?!?!? HOW? WHY? *sobs in a corner* I've read a few good justifications for the...unpardonable thing that occurred in the latter half of HBP but I've still unconvinced. HOW?!?!?
As for fandom. Look around you. You're on livejournal. Unless you're a one-eyed hermit, you'll find enough Harry Potter wank to fuel your hatred of humanity for a whole week! (Pretty damn good deal, if I do say so myself).