I was horrified to read this morning that the upcoming OS update for the iPad will change the rotation lock to a (partial) mute switch. This is a TERRIBLE change. I bought the iPad to use primarily as a versatile ebook reader, and I use the rotation lock every single time I read a book on the iPad. Because I’m often reading while curled up in a comfortable chair or lying in bed, I’m frequently holding the iPad at a 45 or 90 degree angle. “Up” is subjective; if I’m sideways, the book needs to be sideways too — and it shouldn’t re-flow the page every time I sit up to get a drink.
Please reconsider the rotation lock. It’s an essential feature in the iPad reading experience.
(If you’d like to write to Apple about this, here’s the feedback page for the iPad.)