Well it's like all advertised car deals these days. If i see a "*" on that billboard/advert i know:
1. 10% Deposit
2. 30%+ Balloon payment (In this case it looks like 45% balloon)
That's the only way they get the monthly installment so low. So they can call it a "guaranteed trade-back value" or whatever they like, it is STILL called a Residual/Balloon payment.
The interest rate is very good though, but you will get it anywhere (especially BMW likes to do it) if you buy a car under similar terms. You are essentially leasing the car.
So knowing this is a standard deposit+balloon payment type of deal, why not shop around and see whether the deal is really that good?
Thing with balloon payments is, and especially with this deal, if you actually want to keep that car after 3 years, you need to come up with a rather huge amount of cash. Don't make the mistake alot of people did (probably still do) , they buy their cars with balloon agreements and every 3 years they need to trade it in (to pay off the balloon) and they're forced to buy another car. The problem is, everytime you do this your monthly installment is higher and your balloon grows (if you continue to do it like that) . Whereas if you bought a car under traditional terms, you might be paying the same installment for 5-6 years and continue to have ownership of it.
So at the end of the day, you actually never ever manage to own a car outright and your monthly car payments will continue to go up. It's like renting a house vs. buying it.