AOA is useless when not in flight -- ie no angle of attack to measure.
In flight, AOA is and instant source (regardless of weight) for determining:
1. Stall AOA - useful for stall recoveries and max performing the wing in the event of terrain closure or windshear escape.
2. Approach speed
3. Max ANGLE of climb (L/D max)or best holding speed
4. Best range AOA
There are several different types of AOA presentation, such as:
"Normalized" - where the max lift is calibrated as "1" on the gauge. In this case, the corresponding normal approach speed would be about ".6", and L/D max of about "3.2"
Or
"Raw units" calibrated in degrees of angle of attack. In the military aircraft I flew, approach speed was primarily referenced to AOA (in that case 7 units), with flaps down stall at about 16 units.
Many commercial airliners have the info avail but don't display it explicitly. For instance the newer 737s have a tiny little gauge in the CRT while the 767 has a "pitch limit indicator" on the attitude display when the flaps are down.
I like AOA raw presentations. You have to know what you're looking at, but once you do there is a wealth of information there. Depending on if the system display is independent of the CADC, it would be a good backup to total IAS indicator failure.