My 2 cents,
I have done the old school break-in on all my new cars. But even if other feel that is out dated here are some things to consider:
1. During the first few hunderd miles (I think 500, but some say up to 1000), the engine computer is learning how you drive and makeing adjustments. That is a fact that the dealer will tell you. And if you ever disconnect your battery for a long time, it goes through that again. So how do you want your car to learn about how you drive? Personally, I'd want it to be like I driver 80+% of the time.
2. Your car as brand new brakes. You want to break those in a little. So be gentle with your stopping for a few days, at least.
3. As olnycodered said, the rings need to be seated. Do you need 500 miles of that? Maybe not with today's engine, but you want to do for some time.
4. A car is made up of a lot of parts. With today's tech and build procedures, issues are rare, but it can happen. Seems like a good idea to take it easy and make sure things are all tight and in working order.
So I just do the 500 mile thing. It is cool when you hit 500 mile and know you can have fun. I take the time to know the car and understand its quirks.