As people normally say, a picture is worth a thousand words. In Kathy Sierra’s Featuritis Curve there are some words, but the message from the whole picture is more than the sum of the words:

Shmula brought the topic back in his blog, where he mentions a very strong phrase from A.G. Lafley, the CEO of Procter and Gamble, which should be remembered whenever we think about adding a new feature into our products:

People remember experiences. They don’t remember attributes or benefits or features.