Interesting take from Sean Madden at Wired on why the Amazon Fire Phone may be too delightful for its own good.
The average smartphone user interacts with his or her mobile device over 100 times per day, and the majority of those interactions fall into just a few categories: opening an app, selecting from a list, bringing up a keyboard, and so on. If each of them is imbued with too much visual whiz-bang, using your phone becomes the digital equivalent of eating birthday cake for every meal.
I would argue that it's not so much the frequency of the effect but the utility that matters. If the effect slows down the experience without offering anything other than eye candy, it's bad design. “Whiz-bang” is a sparkly coat of paint on the surface of the interface. Delight is the spark of life that lives inside the app, coded deep into its DNA.