What packaging features are important to customers?

The package itself is the most important feature.

Marc Gobé writes about the importance of the packaging in his book called:

"Emotional Branding: The New Paradigm for Connecting Brands to People".

As an example he describes the uniqueness of Coca Cola glass bottle. Even if its shattered and the pieces are all over the floor in a dark room, its possible to tell that it used to be the bottle of Coca Cola.

Thats how important the packaging itself is, that you can notice it and connect with it from the smallest glimpse and touch.