I'm not sure I understand the attraction towards medium-high and low priority standby unless you're single and never travel with anyone; even then it's a crap shoot. Eagle had the best system with the ability to check flight loads, but even then there were always people gaming the system, the methods of which I won't go into here. It was always so much fun to book on a green flight (wide open) and then show up to have it totally in the red (oversold) only a few hours later.
Anyways, it's nice to be able to JS to get yourself to and from work, but other than that... I don't see it as some great benefit.
Just my .02 of course.