Finished (big fat spoilers)

Wow. 10 minutes after I finished it and even though my mind's still reeling (DUMBLEDORE!! SNAPE!!! OMG!!) I'm already speculating.

I can't believe that Snape is actually a Death Eater. He's still a double-agent, I'm convinced. Dumbledore's death is the Order sacrificing their queen. I'm going with the theory that Snape must kill Dumbledore because Dumbledore ordered him to; they're both talented Legilimens, after all. Was not expecting him to be the Half-Blood Prince, however.

Wow. Just, wow. Must get back to reading internet discussions full of wild theories and speculations.