If the USAA car buying service happens to refer you to BMW of Rockville, don't buy a car from them.
They are very aggressive with the up-selling and their maintenance department has a bad track record.
Also, they are really bad at handling things like title transfers and registration paperwork if you don't live in MD. I have had two bad experiences with them that ended up costing me time and money to do paperwork with DC DMV so they didn't have to. They'll hold collateral or deposits hostage until you do the work for them. I was dumb enough to do business with them twice. Never again. If you need more opinions check their Yelp reviews. They are on the "bad" list all over the place because once they get you to sign on the dotted line, they have your money and you're on your own.