Plenty of people have made arguments for used cars, so let me give some for getting a new car:
1. You can get exactly what you want. Depending on the size of your market, there may not be many used cars to choose from that are equipped the way you would like them to be.
2. You can control the care that the car receives. It is important to break a car in properly and maintain it correctly from new. How well do people take care of cars they are planning on trading in a year or two, particularly if they are leasing them? I knew someone who financed a new car, barely made a payment from day 1, and treated it horribly, just waiting for the day that the repo man came.
3. You can finance a new car from now until doomsday at a low interest rate. You can't get as long a term or as low an interest rate on a used car in most cases. Also, if you're looking for a largish family car, chances are the dealers can't give them away with gas at $4.00 a gallon, so you'll get mad incentives to take it off their hands. Used cars were purchased under different market conditions, so every big one is a hardship case where people who are dropping them because of gas prices owe more than they're worth. Why get involved when you can pick up a new one with thousands in discounts?
4. Warranties. Any new car is going to have a decent warranty standard. Warranties for used cars cost thousands of dollars, offsetting much of your savings from buying used in some cases.
These are just considerations. The right used car can still make sense. I often go to look at used cars for friends. You'd be surprised how often I spot signs of abuse and poorly repaired damage that hasn't been reported. I did just help one friend buy a Mazda 3 with 29,000 miles that was all it should be and all it was advertised to be. It was about $6,000 less than an equivalent new one would have been. It was about $8,000 less than one equipped the way she really wanted would have been though, so if money was less of an object a new one still would have been preferrable.