Here's my peeve about writing for middle schoolers (ages 10-14): when it comes to library budgets, review space, and award competitions, our books have to compete with hefty (thematically and word-count-wise) reads targeted for high schoolers. You gotta wonder if adult gatekeepers favor older YA novels because they read more like adult literature, as evidenced by the interesting discussion on author Justine Labarlestier's blog (source: Chicken Spaghetti) and the adbooks listerv.
Exceptions abound of course, but there's a big difference between an eleven-year-old and a seventeen-year-old when it comes to literary appetite, maturity, and attention span. I thought the books nominated for the Cybils in the middle reader category, for example, were perfect for most 8-12 year olds. But in the YA category, it seems odd that Hattie Big Sky (classified by School Library Journal as a middle school read) has to compete with Nick and Norah's Infinite Playlist (which Booklist considers appropriate for grades 10-12) and The Book Thief, which is causing some of the fuss in the YA vs. adult lit debate.