In my experience it boils down to this.
You have to examine if the parks you will visit or in the area's you most often camp at, travel through are PA campgrounds. PA's 50% discount is a much bigger discount than almost any other camping discount. Yes, there are restrictions. Some say only a 2 days, some say only Sunday-Wednesday or Thursday. Some say no holidays. Some have other restrictions.
If your a holiday weekend camper, your likely not going to be able to use the PA discount those weekends. If your a long weekend only camper, again, might not be for you. If your like me and take 3-4 week long camping trips and can save 50% off a $20-$30 a night campsite for Sunday-Wednesday or Thursday, you can see that it pays for itself pretty quickly, generally on the first or second full week camping trip. I have also gone to doing long weekends on Friday night through Monday or Tuesday night which allows me to use it on Sunday and Monday besides the benefit of the campground being less crowded on Sunday afternoon-Tuesday morning.
I also have the Good Sam discount card and most places I camp, allow use of both, just not for the same days fees. So I get 50% off the days the campground allow PA and my Good Sam Discount the days they don't.
It's all about educating yourself about the restrictions on the campgrounds you usually visit, checking availability of PA campgrounds through area's you travel and stay and trying to utilize it when you can. You will find that it's mostly accepted at campgrounds that are seldom at capacity (except holiday weekends) which fits right in with my desire to camp at places that are not crowded.
Anyone not happy with the PA discount program in my opinion didn't take enough time on the front end to research if it fit their style of camping and availability of PA campgrounds in their camping area's. All the information you need to make an informed decision is openly there on their website for all to see without having to sign up first. Do your homework.