I have my mortgage with them. My experience has been OUTSTANDING. When we closed, their rate was the best I could find, the process was very painless, and the service since then has been truly exceptional.
On our first house, we went with a local bank. In a matter of a year, our mortgage was sold 3 times...each time causing billing problems and each time the customer service got worse. USAA typically does not sell loans, and even if they do, USAA still services all of the loans...so it's completely transparent to the customer.
I know it sounds like I've drank too much USAA Kool-Aid, but after spending 6+ months fixing billing errors (and subsequent credit report problems) due to a mortgage company's screw up, there is no way I'd give up USAA's customer service...even if it meant a slightly higher rate.
Lastly...Mover's Advantage is a wonderful program as well. Highly recommend.