IIRC, it seemed clear that the pass did not include last seat availability and was subject to some form of capacity constraints. I bit on the fall/winter pass at $299 thinking if I use it twice on PHX-SAN/SNA it will cost me the same as two one-ways on AA or WN. I was impressed with the current (summer) availability checks I ran from PHX in the last couple of days as well, but time will tell. If I get to CUN or SXM once over the course of the winter, it will have a been a screaming bargain.