I downloaded Avare and played with it for a while. Here are some thoughts.
Ease of downloading and updating all sectionals, charts, plates, diagrams, what have you, etc.
I do not wish to have to click everything separately to got it all; one button labeled "download all" please.
Ability to tap on airport on map to bring up information about airport such as:
comm frequencies, airport facility directory, fuel price, plates available with the ability to select any of those plates.
Ability once a plate is loaded, to toggle back and forth between map and plate.
Ability to search with tabs which display nearby or recent:
airport, vor's, intersections, etc with both identifier and common name
This is useful when in unfamiliar airspace and ATC states go direct (pick your vor navaid or fix name).
Ability to enter a flight plan in standard format.
Ability once a flight plan on airways is entered to select only waypoints at turns to appear in plan. This makes it easier to then enter the plan into the older 430/530 series units which do not have airways.