Just thought of something....
When the students see Dumbledore's hand at the Sorting Feast, Harry wonders why it isn't cured yet, and Hermione says, "It looks as if it's died.... But there are some injuries you can't cure... old curses... and there are poisons without antidotes...."
Is it just me, or does that sound like MAJOR foreshadowing?
Come to that, there were several references to poison in the book, and much is made of the bezoar, which, as we learned in PS/SS, 'will save you from most poisons'. Most, not all. It is ridiculous that, after Ron's near death, Dumbledore wouldn't carry a bezoar with him on a dangerous mission. But he seemed to recognize the sludge in the Horcrux basin, and it was obviously a progressive poison, and the first person he asked for when they got back to the castle was Snape (who had personally prevented the curse on the LAST Horcrux from killing him!!!), and he didn't even mention a bezoar.
I think we'll find that the sludge was one of the poisons that could not be cured.
I think the locket will be found among the stuff Mundungus Fletcher nicked from 12 Grimmauld Place.
I think we'll find that Lily was close friends with Snape -- at least before she married James.
I adore Rowling's prose. It's tight as a drum.
That is all.