I've considered and decided against joining ACA for the immediate future.
I didn't find the sample issue I have read very useful, didn't care for the style of writing and have been able to obtain/examine (partial) sets of some of their maps at "used" costs on eBay/from other riders. I read their forums daily and find little that isn't available elsewhere except for specific information/discussion about their routes/maps. Their online store definitely is not the place to go for low prices. So, for me, for now at least, membership isn't worth the cost.
I definitely put ACA in the same category as LAB for me - it's "nice" that they think they are accomplishing something for bicyclists in general. If they are, I'll benefit from it. But realistically, if they didn't exist, I'm not sure I'd miss them.
If I were riding 3-4 tours a year on "their" routes,then I might look at things differently.
My curmudgeonly $.02