We just finished our first year with CAA and we've saved a ton of money, not even counting the roadside assistance. We got discount tickets to Wonderland (I believe $20 off/ticket), multiple discounts on hotels, discount at the Zoo, etc. And I've had it taken everywhere that takes AAA, so I don't think that's a problem, but I don't know the official policy so I wouldn't want to guarantee it.
Also, one thing I learned about CAA when we joined is that it is attached to the person, not the car. So you don't need to have a car for the roadside things to be useful. Anytime you might need help an an Autoshare car - for instance, recently my husband locked the keys in the car, something that probably paid for the cost of the membership as well, or if you ran out of gas or needed towing, etc - then it would be covered through CAA. Even if you were with a friend in one of their cars, or in a regular rental. I was a member of Autoshare for a while, but I don't remember what their policy is if something like that happens to a member. But if you lock yourself out of the car, I can't imagine that they would pay for you to get back in.
Either way, I definitely recommend it.