@Jaxk As one who has a ton of PDFs on my Nook, I can say that I am glad that I have the ability to lock out screen rotation. It can be done at either the system level or, with the better PDF readers, within the application. However, since you’re probably not running a Nook Color reflashed with CyanogenMod running ezPDF Reader, I’m not sure where you would find those settings, only that it’s something that can be changed.
@rojo I paid less for my Nook Color than I did for the bookshelves that hold all me dead-tree books, though I (okay, my wife) also shopped wisely and paid less than retail for it. Then again, the books I like tend to run $30–60 and are obscure enough to never be found in a used book store anyways. In the end, we must each decide what a tablet/e-reader is worth to us, and we won’t all have the same answer.