I find myself experiencing a disconnect between the books that came out before I read them, and those that came out after I had gotten into HP (namely, 5 and 6). I don't dislike them, I just find reading them to be a bit different. Have you ever encountered people who came to a fandom much earlier or later than you, who have very different opinions of the material? I know some people who didn't see any of the Star Wars movies until the second trilogy came out, and see them as all equally good (or bad). For me, the first three are enshrined in memory, whereas I judge the second trilogy by adult standards, and find them lacking.