I'm a 29 years' long happy customer of USAA for auto, home, and banking services. The service has been great overall (minor hiccups over almost 30 years are to be expected, but they've been minor and properly handled by USAA, IMO). They are very competitive in my state on auto (every so often I call one of the ads "we'll save you up to $500 on your car insurance" and everytime I tell the rep I use USAA currently, they basically tell me that they can't help me).
They've also serviced my account well when I was hit by another (insured) at-fault driver whose insurance company was giving me the run-around. I called up USAA after some exasperation and turned the claim over to USAA who paid it very quickly (and very fairly, far more fair than the other company was proposing) minus my deductible, then subrogated the claim against the other driver and a few months later, also sent me a check for the deductible after that successful action.
Two thumbs up.
My parents also use them, but have dropped them for homeowners as USAA is not competitive in their (slightly hurricane prone) state.
USAA General Agency (aircraft, boat, classic car, etc) insurance is just USAA acting as salespeople for other agencies. I have used them in the past, but would recommend you avoid them (and as a mustachian, would recommend you not buy products which could be insured by the General Agency... ;) )