I found the teenage romance stuff tolerable, although it seemed that several bits came out of nowhere. I don’t remember book 5 well, but I didn’t have an impression that Harry had a crush on Ginny. And his noticing that Ron and Hermione also seemed too sudden.
But the bigger problem with that plot thread is, it didn’t seem to have much to do with the rest of the book. I like it better when all my plot threads braid together. Ditto Remus and Tonks: why should I care?
And yeah, I cried at the end. I’d avoided spoilers, but there were enough not-so-vague references floating around that it was pretty obvious Dumbledore was not long for the world. I did not expect to go the way he did, though. And if he hadn’t frozen Harry, then Harry might have been able to stop Draco in time for Dumbledore to get his wand and do … something. But whatever.
Snape. I do not know what to think about Snape. Could go either way, still. I do think Dumbledore wanted Snape to kill him. Some people have speculated that he didn’t want Snape to break cover; that seems weak. Maybe he didn’t want them to take him prisoner; but they weren’t going to. And asking Snape to do it just so Draco wouldn’t – well, I’m sure any Death Eater would have obliged. Why Snape?
Oh, I am an idiot and did not link Half Blood Prince = Snape, despite the ability at potions. Duh. I was thinking Voldemort, actually.
I have no theories on Harry being a Horcrux. While that would be really interesting, creating a horcrux by accident seems weird; how many murderers would have done it?