USAA has a big and loyal following. Most of it is deserved.
Caution: Some people say USAA car insurance is the cheapest but many do not compare. The truth is that they are often the cheapest but not always the case. My guess is that they are the cheapest 80% of the time.
Their service is good. I know of two people that made a claim. Both were paid fairly. However, one of them was paid by another insurance company with USAA only helping the process since the driver who was wrong had another insurance.
At the end of the year, they used to send a little check/refund which they called a dividend. Now they save money and just apply it to your next premium unless you ask for a check.
One drawback is that USAA does not insure everyone. They only insure military people or kids of military people (it's ok if Dad was in the military decades ago). Their requirements are less strict than before (when you used to have to be on active duty to qualify)