I too have "free" Priority Pass membership, through a charge card. I have often made use of it, and in some cases the lounges that it gives access to are in fact better than the lounge of the airline I am travelling on.

Sometimes, though, there is no lounge, even in quite big airports, and sometimes the lounge is in another part of the airport and so is inaccessible (for practical purposes). But that's just the luck of the draw, I guess.

I don't think that they programme covers non-international lounges, but I don't know that for a fact.