Features of a product can be classified as
1. Table stakes: features the product must have otherwise people won’t buy (e.g. phone service in iPhone)
2. Incremental: the more the better (e.g. capacity)
3. Delighters: users don’t expect but feel happy (and willing to buy)
Source:
http://www.good.is/post/object-lessons-from-the-iphone-s-dropped-call-problem/