Eh, I use both the Nook and Kindle apps for my iPad -- daily -- and Nook is just as good. It's the hardware. If i wanted to buy an e-reader, i wouldn't want to invest in B&N hardware.
Unlike the Kindle with its proprietary format, the Nook reads standard ePub files. Even if B&N went out of business tomorrow, the Nook would remain a perfectly usable device.
