I use the discount at our Pearle Vision every time we buy glasses (and all 4 of us need them). They compute my different discount options - one via my medical plan, one using their current ad promo, and the AARP one. AARP always ends up being the cheapest for me.
We also use them for hotel discounts. And I guess I should more closely review the discount list!
Their magazine is OK, but I really like the small "newspaper" style piece we get as well. That often has pieces of info that are useful to us, especially as we help my MIL with her issues. For example, reminders about the timing to sign up for next year's drug plan (dates changed this year), the link on where to compare the various plans and costs, etc. Having that info has been worth the membership to us.
I've also worked with AARP as a potential partner when I was employed at a big consumer products company. They clearly know the value of the access they can provide to their huge membership, a demographic that more companies are starting to value for its disposable income. As someone who pays dues, I get annoyed that I'm bombarded by all the promotions from their partners. I know that because a company is "AARP connected" doesn't necessarily make them the best value, but I suspect there are many seniors who don't recognize that. I belong to other membership organizations that do that same thing, but someone the AARP stuff bothers me more.