I am fine with AARP's ideology, but I have not found a membership to be of any benefit to me. I've joined twice, but have not used the discounts enough to justify membership because either I was unaware (popcorn at the movie theater? Didn't know!) or, more often, I've gotten better discounts on my own or through AAA. I also don't use AAA discounts as often as I could for the same reason. I can't keep track of what they are!
I think if, like me, you live in a rural area and don't find benefit in their travel discounts, it's not really worth it. However, the cost is minimal so it doesn't hurt to try it out.