As far as AUs, I've learned to appreciate them. I originally didn't want to read anything that wasn't about The Backstreet Boys being "The Backstreet Boys," but I read a couple of good ones for Mare's old fanfic discussion group, Between the Lines and On the Outside, that changed my mind. I loved those two stories because, even though the Boys weren't "The Backstreet Boys," they still seemed like themselves, in terms of personality, and the brotherly bond was there or developed through the story. To me, that characterizati on is crucial in an AU. They don't have to be famous singers, but they should still seem like Brian, Nick, AJ, Howie, and Kevin.
I wrote my first AU back in like 2001 at the request of someone who gave me the idea; it was one of those "Brian has a long lost sister" types (except he was actually the long lost brother who'd been abducted), and I hated it. Code Blue really opened me up to writing AUs; I hated the idea of it at first, too, but I gave it a shot and ended up loving writing that story. 00Carter and Song for the Undead have been some of the most fun stories to write, and they did so much for my opinion of AUs that I'm now writing one on my own, Secrets of the Heart, and enjoying that too.
What I love about writing AUs is the complete creative freedom it allows. It's definitely a bridge between fanfic and original fiction, because even though you're still using the same characters, you can make them seem more like original characters by putting them in different lives. I will always prefer writing the guys as BSB, but it does sometimes get tedious writing about the music business, touring, recording, being famous, and all of that. Sometimes it's nice to put them in a world where all of that isn't part of their lives, where they can be doctors or secret agents or survivors of the zombie apocalypse or just normal people. It's like playing dress-up.
In terms of reading, I still much prefer canon BSB stories, but I've read enough good AUs to not be turned off by a story simply because it's AU. If I can still recognize the guys as themselves, and the plot sounds good, then I'll give it a shot.