Great deal, I bought one 4 years ago after my tour in Japan. Walked into the office, filled out the order form and dropped a check from Navy Fed, easier than ordering sushi. I was in the office for about 20 minutes, ordered a custom built BMW for straight-up invoice price and walked out... no haggling, no pressure. The price for the car was exactly as listed on Kelly Blue Book as the invoice price. We had it delivered to Virginia Beach and picked it up when we got back to the states, about 4 months. We were even able to track it online as it was built. Comparing it with dealer prices, we saved about 8K and got exactly what we wanted. We're hoping for overseas orders again so we can upgrade it.
Just make sure it's an actual BMW factory dealer, some of the off-base "military sales" places are just private dealer storefronts that cater to US military. If you can't get invoice price and have to negotiate, it's definately not legit.