There are a lot of postings here about PP but no specific thread.
My advice would be to check the web site of the airport(s) you're visiting and see if their Priority Pass lounge has "pay-per-use". Most do. So, if you don't want to fork out the whole membership, you can just pay 1-2 entry fees. The ones I've seen/used in the past cost between USD18-30, depending on the country and services offered.
If you travel a lot, the membership option represents great value.