I think the hacker cred had the most influence in what happened this week. If Rowling (or her publishers) hadn't made such a big deal of never authorizing digital editions previously, the efforts to convert the books more and more quickly might not have escalated to the point that the hackers felt that they had to get the digital edition out before the actual paper edition to outdo the 24 hour turnaround last time.
I don't think reading the first chapter out loud to the waiting line is that bad, though I don't know how the people in line felt. After all, they'd have the book shortly. It's not like reading the LAST chapter to them. Nice way to spend waiting in line, if you ask me. At least, if the reader has a good reading voice and style.
As far as why I like the books so much, I like the characters, and the fact that the characters who succeed do so because they are basically decent, in a very credible way. I also like the way Rowling tends to work in plot twists-- she does keep you guessing, right up to the end. I won't provide specific examples because if you're considering reading these, it would take a lot of fun out of the stories. I will say that I was satisfied with the final book. I wasn't sure how well she would carry off the conclusion, but I think she did it, and did it well.
As far as plot holes, well, she does have trouble with some details, like how many students there are at the school, but they don't interfere with the telling of the story.