...behind the cut, of course.
Dumbledore's death -- was dramatically inevitable. Given that Harry is the hero of the series, the "one wizard Lord Voldemort ever feared" has to be out of action before the final book, so that the responsibility for the Dark Lord's ultimate defeat or ultimate victory is in Harry's hands. Also, the death was probably something planned out in advance, though perhaps not in complete detail, by Dumbledore. Why else take no one along on the final adventure except Harry, and why else swear him to complete obedience?
Snape's betrayal -- is almost certainly not entirely what it seems. Snape is not Harry's Big Ultimate Antagonist, any more than Draco Malfoy is; the main thrust of book seven has got to be "Harry versus Voldemort", not "Harry versus an annoying schoolmate and a teacher he never liked." Lesser adversaries than the Dark Lord are being cleared away from the plot, not added -- Wormtail makes barely a token appearance; Lucius Malfoy is nowhere in sight; Kreacher has been shuffled off to work in the Hogwarts kitchens under Dobby's watchful eye; even the Death Eaters, while increasingly active, are mostly doing their Death Eaterly deeds offstage. Also, Rowling has been doing a carefully choreographed fan dance with Snape's backstory and motives all along: first he hates Harry; then he saves Harry because he owes James Potter a life debt; then he's revealed as an ex-Death Eater and a double (and therefore possibly triple) agent; then we discover that he came from an abusive home and was the target of bullying on the part of James Potter and Sirius Black during his school years. It would be uncharacteristic, at this point, to have had the big definitive reveal on the subject with an entire book's worth of plot to go.
The action at the climax -- we may not yet know everything that actually happened. We do know from Goblet of Fire that Rowling likes to do action set-pieces which turn out, later, to have had other stuff going on besides what the viewpoint characters saw, and where the true interpretation of observed events turns out to be something other than what we were initially led to believe.
Draco -- annoying, as I said, and cowardly, and the world's most incompetent would-be murderer. But he has, so far, not gone across the line, and may still be a redeemable character. Or, at the very least, a character sufficiently not-evil so as to still be standing at the end of the series.
Slughorn -- probably not evil, but I suspect insufficiently good. Entirely too fond of power and influence, and probably buyable with cash and creature comforts. And one should not forget that it was on his watch that Tom Riddle first turned Slytherin House into a nest of Death Eaters.
Tom Riddle -- downright creepy. Rowling's worked bits of classic serial-killer pathology into this portrait of Voldemort as a young man, including the way he got his start in tormenting small animals, and the way he likes to collect "souvenirs". The story of the two younger orphans he took into the cave is also extremely creepy. And the lake full of bodies recalls, unpleasantly, a killer's hidden victims.
(There's an interesting three-way parallism going on, too, with Riddle, Snape, and Harry -- all three had unpleasant or abusive childhoods, though Riddle, who turned out the worst, seems to have gotten off the easiest of the three of them. The Muggle orphanage as seen in Dumbledore's memories appears bleak and unappealing, but not actively hellish; young Tom's room is certainly more comfortable than a cupboard under the stairs.)
Albus Dumbledore -- a bit creepy at times in this book, as well. (That blackened and withered arm makes an uncomfortable parallel with Wormtail's silver arm, just for starters.) His goals and motives are even more obscure than they were before, and his methods sometimes seem a bit dubious -- putting Harry up to the job of getting Slughorn's deliberately obscured memories seems a bit "off" to me, somehow, though it's in line with his earlier use of Harry as bait to draw Slughorn into teaching at Hogwarts. Given the emphasis in this book (and throughout the series) on changed and illusory appearances, I almost wonder whether we may be scheduled to find out that Dumbledore was actually Voldemort, or a horcrux-produced fragment of the Voldemort persona, all along in this book. If I could just figure out a plausible reason for a Voldemort-avatar to feed Harry Potter the Tom Riddle backstory, and could figure out why a Voldemort-avatar might need to uncover Slughorn's self-obscured memories of an incident Tom Riddle was present at the first place, then I'd be in business.
thoughtful