I'm a finance guy, so I wanted to throw my 2 cents in.
The idea of this balloon plan is to simulate the payments you would have if you had a trade-in or down payment when you bought the car. Basically, Mazda loans you a down payment, and after 60 months you pay it back in one lump sum. You are counting on the fact that the car is worth enough 5 years from now to pay off the balloon. The plus side is that your payments are lower, the minus side is that when you go to buy your next car, you also won't have a down payment/trade-in to lower the payments on your next loan.
I haven't seen the numbers, but I'd guess this is a good deal (compared to a lease) if you take care of your car and don't put too many miles on it. In that case, the trade-in value of the car will be worth more than the balloon payment, so you will have some money left over. If you put a lot of miles on your car, your car will be worth less, and you may have to put some money into the balloon payment.
Some things to consider: If you decide to keep your car after 60 months, all you have to do is find a bank that will refinance the balloon payment. Then you can keep making payments until the car is totally paid off. Here's another thing - Don't wait until the last minute (5 years from now) to trade the car in and pay off the balloon The salesman at the dealership will probably give you a very lowball offer for your car because he knows you need to sell in a hurry.