I have insured with USAA since 1972. My first vehicle with them was a 1973 SAAB 99 that we drove for three years while I was an Army dental officer in West Germany. Our residencies and autos have continuously been insured with USAA, and I believe that our only claim was when I whacked a deer with my wife's minivan a few years ago. They were great to work with. No complaints. However, I do believe that their rates may have become significantly less competitive over the years and the service is a bit less then in years past. One complaint that I have is that after I purchase a new car I find that as the car ages the insurance rate fails to decline as much as I would expect, considering the fact that the replacement value of the vehicle has obviously declined significantly.
A few years ago the government made USAA change their pool of insured. Originally USAA membership was limited to past and present commissioned and warrant officers. I can't say exactly when, but a few years back USAA had to open membership to anyone of any rank that had served in the military, as well as their sons and daughters.
This may sound a bit cold, but the fact of the matter is that the risk pool changed quite significantly with that membership change and it eventually was reflected in rates. One caveat with USAA however, is that each year members get back a portion of what they have paid in (based on financial results), and that reduces the net cost of insurance to some degree. So if you are eligible you need to take that into account.