Son says you can hook up headphones to do any normal format audiobook. I haven’t done this yet myself as I’m not good with audiobooks. No WMA support, but it will play MIDI. Pandora is loaded on the Nook Color out of the box. The speaker isn’t terribly loud but it could be worse. I annoyed a son last week with game sounds, anyway, and had to turn the sound down!
The screen size for pdf’s isn’t too bad if you turn the nook sideways and then size the page so that the text just fits in the 7in the long way and it works for these middle-aged eyes. Not too much trouble. It is harder if you try to read one “upright” I happily read my version of “Hearing and Reading, Telling and Writing” in this way and did just fine. So it works well for me.
There are ways to get calibre to convert Kindle books, but all of them are technically illegal, as they involve removing the books’ inbuilt DRM (Digital Rights Management), which restricts copying and converting to protect copyrights. Rooting it allows you to install the Kindle reader. Took son about an hour or so. Ds says he’ll send a step by step if someone wants to root one.