Just my opinion on AOA instrumentation. First, I have one (Dynon) and really like it. Second, it uses an audible beeping sound that gets progressively more intense until it becomes a solid tone at incipient stall. Without the audible tone it would be useless to me. The Dynon also has the multi-colored visual indicator on the panel, but when I am on very short final I have no time to take my eyes from outside and look down at the panel. I guess some folks with visual indicator only are satisfied with it, but I believe most of them have it mounted up on top of the glare shield or in some type of HUD.