Both my husband and I used AAA for many years. It's a great service- the prices are reasonable and the service is quick and reliable.
The plus side to AAA is that is is very portable. We've moved to 3 different states in the last 2 years, and AAA just requires a change of address. We've also had consistently good service in all three states. It also offers travel and car rental discounts that are not available to non-members. There have been times when I was able to reserve a room and rental car through AAA when there were no cars or rooms available through other websites (hertz, thrifty, orbitz).
I am not sure how it compares with regards to other companies, though.