On the Citation I used to fly many years ago there was an excellent AoA meter and we found that with a little practice we could determine the weight of the plane in-flight to within 100kg, and by using the meter the other way we could get our speed accurate to within a few knots as well on departure and approach.
I'd love to see them fitted and used more often in larger aeroplanes, and also used in the sim in emergencies. They take a little getting used to, but once you do they are fine.