I have one of the
Alpha System Lift Reserve Indicator
, and had it installed on my STOL Cessna 150 for a while. I am very impressed with the concept, and experimented quite a lot. What I found though was that my aircraft was capable of flight speeds which were slower than the apparent capability of the system. The pointer just kind of wallowed at low speeds, I suppose because the total dynamic pressure was not quite enough to activate the indicator, so the differential could not be measured diffinatively. I found I could get airborne before I had certain a "fly" indication. It thus left me not totally confident about the information provided on approach at low speeds (the whole reason for having it). Thus I removed it, and it remains on the shelf.
That said, I am still quite impressed with it. On a faster aircraft it would probably work very well. I have a 182 coming up, which perhaps I will experiment on.
As for my 150, I will continue to use a combination of the ASI, and "the force!" on approach. The results are very much to my liking!