In a search for “nook” the B&N device comes up second, after a comparison “feature” article (not even a product result.) Now look at the product category, “office products”. (Lambaste, lambaste.)
A search for “ipad” again yields the second-place treatment.
The chief benefit is that it distributes the processing load from your main workstation to an external device.
The go-to music sources all have mobile apps (Pandora, Spotify, iTunes, Rdio, &c.) My favorite underdog music service of the moment is still Dragontape. Create and listen to (watch) user-generated YouTube music video playlists. Compose “tapes” on an iPad, iPhone or in a PC browser.