I not only use it but had the privilage to be taught by the man himself. It works very well on everything I have flown from C152 to the MD83..including a few years flying into PNG airstrips..never once have I thought of the mathematics of it..thats for the classroom..Constant aim point..throttles for speed..Flare when aim point is out of view..new aim point horizzon..result = aeroplane lands itself..I have taught this to many young pilots and everyone comes away happy and more confident.
And for those that dont know Capt Jacobson is a very experienced Airline Training captain..
Now all you GA experts can pull my comments to pieces if you like but the facts remain the same..