My PP membership has first 3 visits free per annul and $27 per visit thereafter. The membership fee ($99/year) is covered by annul fee ($125/yr) with the credit card.
While browsing thru the list of participating lounges, it appears PP coverage might be better (more useful) for frequent international travel than domestic travel. Nevertheless, its still worth considering to keep, especially when the first 3 visits are free :-)
You are absolutely right in that the most helpful feature is probably ready access to lounge agents.