I purchased AAA years ago and had it as a safety net (mainly for towing). After a few years of not using it I let it lapse. Not a week later, my wife her keys in her car. The locksmith cost more than the AAA yearly membership!. SO, needless to say we got it again.
Discounts are so-so. However, while we lived in SoCal the benefits were pretty good. Besides the roadside stuff (we will use towing once in a great while), a little known secret was that the local office also housed a mini DMV. For those of you who have been to a SoCal DMV with the eternal waiting and myriad lines, the AAA office was a godsend. You'd just pop in, take a number, wait a couple of minutes max, and be on your way in no time. Also, the helped with free maps and trip tic's which helped (before we all had gps)... Additionally, as a member you also got good home/auto insurance discounts. I paid cheaper premiums on my house and cars in SoCal than I do in the mid-west!!!
Another thing is that I was able to upgrade my membership, on the fly when I ran into a situation where I needed more miles on the towing. I paid over the phone and was good to go.
They even activated a "new" membership for my sister through my fathers membership when she was broken down on the highway in the middle of a storm. Tow truck came out and everything was taken care of.
AAA is one of those things I don't even think about anymore. I always have it and recommend it to everyone I know.