Positive feedback could be:

Utility: content - provides content and functions that both lead to the goal of usage.  What useful functions and contents have to be provided?

Joy of Use - If the user enjoys the design, he wants to use it more intensively and more often.  What useful functions and contents have to be provided?

Usability -Usability deals with how well a product can be used. Design and Psychology, for example, if users can find the information they want and how long this will take them. if the appearance and content of a navigation bar makes sense and is consistent all over a website. Ease of use. Users should have no difficulties, when they utilize a product. Efficiency is the measure of how fast a goal can be reached. effectiveness - If aims are not reached at all or only in parts, the product is not effective.A comfortable product avoids steps that are an unnecessary strain for the user. Consistency means that similar functions should look and work similarly;

Accessibility - The app is incompatible with Android 2.2.x (for example)