My Nook Simple Touch meets 3 of your 4 criteria, but fails regarding PDFs. My partner, however, has a Nook HD tablet(still at the crazy-good price of $129) that he has been extremely happy with in regards to battery life and features. He feels that the battery life, with the wifi disabled, is fairly close to his old Simple Touch. He uses the tablet online a lot, which is why he switched to a tablet from the basic Nook, so it is hard to judge, he says.

Remember that if you are near a Barnes & Noble, you can poke at the display copies and see how they perform. For the Kindle series, Staples office supply locations usually have floor models.